1. Which of these equations represents the electron affinity of chlorine?

A Cl2(g) + 2e– → 2Cl–(g)

B Cl2(g) – 2e– → 2Cl–(g)

C 21

Cl2(g) + e– → Cl–(g)

D Cl(g) + e– → Cl–(g)(Total 1 mark)

2. Which of these equations represents the second ionization of magnesium?

A Mg+(g) →Mg2+ (g) + e–

B Mg(g)→Mg2 + (g) + 2e–

C Mg+(g) + e– → Mg2+(g)

D Mg(g) + 2e– → Mg2+(g)(Total 1 mark)

3. The sketch graph below shows the trend in first ionization energies for some elements in Periods two and three.

Select, from the elements A to D, the one that

1

(a) has atoms with five p electrons.

A

B

C

D(1)

(b) is a member of Group 3.

A

B

C

D(1)

(c) is likely to be very unreactive.

A

B

C

D(1)

(d) normally forms four covalent bonds per atom.

A

B

C

D(1)

(Total 4 marks)

2

4. Which of these ions has the greatest ability to polarize an anion?

A Ba2+

B Ca2+

C Cs+

D K+

(Total 1 mark)

5. Which of these electron density maps best represents the bonding in the compound lithium iodide, LiI?

(Total 1 mark)

3

6. Which of these statements is incorrect?

A The atomic radius of metals increases down a Group.

B The trend in the melting temperature of successive elements across Period 2 is similar to that in Period 3.

C A metallic structure is held together by attractions between metal atoms and delocalized electrons.

D Na+ and O2– ions are isoelectronic.(Total 1 mark)

7. Which of these statements about carbon-carbon double bonds is false?

A The two ends of a molecule cannot rotate relative to each other, about the axis of the double bond.

B They are twice as strong as a carbon-carbon single bond.

C They have a higher electron density than a single bond.

D They consist of a sigma bond and a pi bond.(Total 1 mark)

4

8. This question is about the properties of ions and ionic compounds.

(a) Solid calcium carbonate, CaCO3, has a giant ionic structure.

(i) Draw a diagram (using dots or crosses) for a calcium ion. Show ALL the electrons and the charge on the ion.

(2)

(ii) Complete the electronic configuration for a calcium ion.(1)

1s2......................................................................................................................

(iii) Would you expect a calcium ion to be bigger, smaller or the same size as a calcium atom? Give TWO reasons to explain your answer.

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(iv) Explain why ionic compounds have relatively high melting temperatures.

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5

(b) Changes in the concentration of ions in a solution can be estimated by measuring the electrical conductivity of the solution.

(i) Explain why solutions of ions are able to conduct electricity.

...........................................................................................................................

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(ii) Suggest why aqueous solutions of calcium chloride, CaCl2(aq), and barium chloride, BaCl2(aq), of the same molar concentration, have different electrical conductivities.

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(iii) 1 kg of a solution contains 0.100 mol of calcium ions, Ca2+.

What is the concentration of the calcium ions by mass in parts per million (ppm)?

[Assume the relative atomic mass of calcium is 40.](2)

..............................................ppm

6

(c) Some buildings are made from limestone, which is mainly calcium carbonate. Gases in the atmosphere such as sulfur dioxide, SO2, and nitrogen dioxide, NO2, can be responsible for damaging these buildings.

Describe how these gases come to be present in the atmosphere and explain how they candamage a limestone building.

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(d) The lattice energy of calcium chloride, CaCl2, is –2258 kJ mol–1 based on an experimental

Born-Haber cycle and –2223 kJ mol–1 based on theoretical calculations.

Would you expect its bonding to match the ionic model? Justify your answer.

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.....................................................................................................................................

.....................................................................................................................................(1)

(Total 15 marks)

9. This question is about bond angles.

A 90°

B 104°

C 107°

D 109.5°

Select, from A to D above, the most likely value for the bond angle of

7

(a) HCH in methane, CH4.

A

B

C

D(1)

(b) FSF in sulfur hexafluoride, SF6.

A

B

C

D(1)

(c) FOF in oxygen difluoride, OF2.

A

B

C

D(1)

(Total 3 marks)

10. Consider the following compounds, P, Q, R and S.

CH3CH2CH3

Compound P Compound Q

8

CH3CH2CH2CH2Br

Compound R Compound S

The boiling temperatures of compounds P, Q, R and S increase in the order

A P Q R S

B R S P Q

C Q S P R

D Q P S R(Total 1 mark)

11. Buckminsterfullerene has the formula C60. Its structure is shown below.

The bonding in buckminsterfullerene is similar to the bonding in graphite.

Which of the following is true?

A All the bond angles in buckminsterfullerene are 120°.

B The melting temperature of buckminsterfullerene is higher than that of graphite.

C There are delocalized electrons in buckminsterfullerene.

D On complete combustion, buckminsterfullerene forms carbon dioxide and water.(Total 1 mark)

9

12. Which of the following compounds shows hydrogen bonding in the liquid state?

A Hydrogen bromide, HBr

B Hydrogen sulfide, H2S

C Silane, SiH4

D Ammonia, NH3(Total 1 mark)

13. Which of the following molecules is polar?

A Carbon dioxide, CO2

B Beryllium chloride, BeCl2

C Ammonia, NH3

D Boron trifluoride, BF3(Total 1 mark)

14. The electronegativities of four pairs of elements are given below. Which pair would form the compound with the greatest ionic character?

A 0.7 and 4.0

B 0.7 and 3.5

C 1.0 and 4.0

D 0.8 and 2.8(Total 1 mark)

10

15. Which of the following successive ionization energies (values in kJ mol–1) could have come from a transition element?

A 496 4563 6913 9544 13352 16611 20115 25941

B 590 1145 4912 6474 8144 10496 12320 14207

C 717 1509 3249 4940 6985 9200 11508 18956

D 2081 3952 6122 9370 12177 15239 19999 23069(Total 1 mark)

16. Which of the following gives the electronic configuration for chromium and for the Cr3+ ion?

Cr Cr3+

A [Ar]3d44s2 [Ar]3d34s0

B [Ar]3d54s1 [Ar]3d24s1

C [Ar]3d54s1 [Ar]3d34s0

D [Ar]3d44s2 [Ar]3d14s2

(Total 1 mark)

17. The hexaaquacopper(II) ion, [Cu(H2O)6]2+, is blue because the water ligands

A split the p-orbital energies and p-p electron transitions emit blue light.

B split the d-orbital energies and d-d electron transitions absorb all but blue light.

C split the p-orbital energies and p-p electron transitions absorb all but blue light.

D split the d-orbital energies and d-d electron transitions emit blue light.(Total 1 mark)

11

18. Glycine, H2NCH2COOH, is a solid that has a melting temperature of about 250°C, and it is verysoluble in water. This is because of the

A formation of intermolecular hydrogen bonds in the solid and hydrogen bonds with water.

B formation of H3N+CH2COO– ions which interact strongly with each other in the solid andwith water.

C dissociation of the molecule to form H2NCH2COO– and H+ ions in the solid and the solution.

D protonation of the molecule to form H3N+CH2COOH ions in both the solid and the solution.

(Total 1 mark)

19. More than half of the elements in the Periodic Table are transition elements. Vanadium, element 23, is a typical transition element.

(a) (i) Give TWO properties shown by vanadium compounds that are characteristic of transition metal chemistry, other than variable oxidation state.

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...........................................................................................................................(2)

(ii) Vanadium(III) ions in aqueous solution exist as [V(H2O)6]3+.

Draw this ion so as to clearly show its shape. Name the type of bond between the ligand and the vanadium ion and state the feature of the ligand that enables this bond to be formed.

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12

(b) Vanadium ions exist in oxidation states from (V) to (II).

(i) Use your data booklet (page 15) to find the standard electrode (reduction) potential

for the reduction of vanadium(IV), VO2+, to vanadium(III), V3+.

...........................................................................................................................(1)

(ii) Explain the term disproportionation.

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(iii) Use your answer to (b)(i), and the data below, to calculate EӨcell for the formation

of vanadium(V) and vanadium(III) from vanadium(IV) in acidic solution. State if the reaction is feasible under standard conditions and justify your answer.

VO2+(aq) + 2H+(aq) + e– VO2+(aq) + H2O(l) EӨ = + 1.00 V

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(Total 10 marks)

13

20. The isotopes of magnesium, Mg2412 and Mg25

12 , both form ions with charge 2+. Which of the following statements about these ions is true?

A Both ions have electronic configuration 1s2 2s2 2p6 3s2.

B Mg2512 2+ has more protons than Mg24

12 2+.

C The ions have the same number of electrons but different numbers of neutrons.

D The ions have the same number of neutrons but different numbers of protons.(Total 1 mark)

21. The first ionization energies, in kJ mol–1, of four elements with consecutive atomic numbers are shown below.

A 1680

B 2080

C 496

D 738

(a) Which element could be an inert gas?

A

B

C

D(1)

(b) Which element could be X in a covalent compound with formula HX?

A

B

C

D(1)

14

(c) Which element could be Y in an ionic compound with formula YH2?

A

B

C

D(1)

(Total 3 marks)

22. The graph below shows the second ionization energy of a series of elements with consecutive atomic numbers.

Which element could be lithium?

A

B

C

D(Total 1 mark)

15

23. The first five ionization energies, in kJ mol–1, of aluminium are

578 1817 2745 11 578 14 831

The orbitals from which the first five electrons are removed during ionization, starting with the first electron, are

A 1s 2s 2p 3s 3p

B 1s 1s 2s 2s 2p

C 3p 3s 2p 2s 1s

D 3p 3s 3s 2p 2p(Total 1 mark)

24. Going across Group 1 from sodium to aluminium

A the melting temperature increases.

B the radius of the atom increases.

C the radius of the metal ion increases.

D the bonding in the element changes from metallic to covalent.(Total 1 mark)

25. Going down Group 1 from lithium to rubidium

A the radius of the atom decreases.

B the radius of the ion decreases.

C the first ionization energy decreases.

D the polarizing power of the ion increases.(Total 1 mark)

16

26. A drop of concentrated nickel(II) sulfate solution, which is green, is placed on moist filter paper on a microscope slide and the ends of the slide are connected to a 24 V DC power supply. After ten minutes,

A a blue colour has moved towards the negative terminal and a yellow colour towards the positive terminal.

B a blue colour has moved towards the positive terminal and a yellow colour towards the negative terminal.

C a green colour has moved towards the negative terminal but there is no other visible change.

D a green colour has moved towards the positive terminal but there is no other visible change.

(Total 1 mark)

27. The bonding in magnesium oxide, MgO, is

A ionic.

B metallic and ionic.

C ionic and covalent.

D metallic and covalent.(Total 1 mark)

28. Which of the following bond angles occur in a molecule of ethanol, C2H5OH?

A 90° and 180°

B 104.5° and 180°

C 104.5° and 109.5°

D 109.5° and 120°(Total 1 mark)

17

29. Which of the following molecules is linear?

A Carbon dioxide, CO2

B Sulfur dioxide, SO2

C Water, H2O

D Methanal, HCHO(Total 1 mark)

30. Which of the following molecules contains polar bonds but is not a polar molecule?

A Chlorine, Cl2

B Hydrogen chloride, HCl

C Trichloromethane, CHCl3

D Tetrachloromethane, CCl4(Total 1 mark)

31. Which of the following has dipole-dipole interactions between its molecules, but no hydrogen bonding?

A Methane, CH4

B Methanol, CH3OH

C Ammonia, NH3

D Hydrogen iodide, HI(Total 1 mark)

18

32. Which list below shows the compounds in order of increasing boiling temperature?

A CH4, HCl, HF

B HF, CH4, HCl

C HCl, HF, CH4

D HF, HCl, CH4(Total 1 mark)

33. Which of the following has the highest boiling temperature?

A Pentane, CH3CH2CH2CH2CH3

B Hexane, CH3CH2CH2CH2CH2CH3

C 2-methylbutane, CH3CH(CH3)CH2CH3

D 2-methylpentane, CH3CH(CH3)CH2CH2CH3(Total 1 mark)

34. Chlorides of Group 1 elements produce coloured flames when

A electrons become excited to a higher energy level.

B excited electrons move from a higher to a lower energy level.

C an outer electron leaves the atom.

D electrons move between the negative and positive ions.(Total 1 mark)

19

35.

Fuel from the air?

A new catalyst that can break down carbon dioxide gas could allow us to use carbon from theatmosphere as a fuel source in a similar way to plants.

Plants break the stable bonds in carbon dioxide during photosynthesis. In the natural process,the carbon dioxide molecule is initially bonded to nitrogen atoms, making reactive compounds called carbamates. Carbamates are derivatives of carbamic acid, NH2CO2H. These compounds can then be broken down, allowing the carbon to be used in the synthesis of other plant products such as sugars and proteins.

A new catalyst produced by scientists is a graphite-like compound made from flat layers of carbon and nitrogen atoms arranged in hexagons. Carbon dioxide binds to the catalyst and takes part in the following reaction, which occurs at 150°C and at about three times atmospheric pressure.

C6H6 + CO2 → C6H5OH + CO

benzene phenol

Carbon monoxide can then be used to make liquid fuels such as methanol.

The energy required for photosynthesis comes from light, and experiments are now going on to develop a light activated catalyst which could break down carbon dioxide in a new process.

(Source: adapted from an article from the NewScientist.com by Tom Simonite, March 2007)

(a) Why are the bonds within a layer of carbon atoms in graphite stronger than the bonds between the layers of carbon atoms?

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20

(b) The data below gives the relative electrical conductivity of a pure graphite crystal.

Relative conductivity in plane ofcarbon hexagons

Relative conductivity perpendicular toplane of carbon hexagons

3.7 0.0017

Explain why the relative electrical conductivity of graphite differs with direction.

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(c) Suggest why the strength of the bond between the layers in graphite would increase if some carbon atoms were replaced with nitrogen atoms.

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(d) Suggest ONE benefit of using a light activated catalyst for the new process.

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(e) The liquid fuel, methanol, is made by reacting carbon monoxide with hydrogen.

Write an equation for this reaction. State symbols are not required.(1)

21

(f) Benzene, which is needed for the new process of breaking down carbon dioxide, can be made from coal. It is now usually made by catalytic treatment of one fraction of crude oil at temperatures of around 500 °C and 20 atmospheres pressure.

Suggest the benefits and disadvantages of breaking down carbon dioxide using benzene and the catalyst as described in the passage. You should consider

• the energy and resources needed

• the effects on the atmosphere

• whether it is a beneficial method for producing energy compared to direct use of fossil fuels.

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(g) Carbon exists in forms other than graphite. Nanotubes are rolls of graphite layers, and fullerenes are cages of carbon atoms. Both nanotubes and fullerenes can trap other substances in their structures, and fullerenes can be coated with other substances.

Give ONE application of carbon nanotubes or fullerenes which exploits this behaviour.(1)

(Total 15 marks)

22

36. The nucleus of a Na2311 atom contains

A 11 protons and 12 neutrons.

B 11 protons and 12 electrons.

C 23 protons and 11 neutrons.

D 23 protons and 11 electrons.(Total 1 mark)

37. The mass spectrum for a sample of a metal is shown below.

The relative atomic mass of the metal is

A 63.2

B 63.4

C 63.6

D 64.0(Total 1 mark)

23

38. The first five successive ionization energies of an element, X, are shown in the table below.

Ionizationenergy

first second third fourth fifth

Value

/ kJ mol–1590 1100 4900 6500 8100

Which ion is X most likely to form when it reacts with chlorine?

A X+

B X2+

C X3+

D X4+

(Total 1 mark)

39. Which of the following substances, obtained from the fractional distillation of crude oil, has the lowest boiling temperature?

A refinery gas

B kerosene

C diesel oil

D lubricating oil(Total 1 mark)

40. Which pair of atomic numbers represents elements which are both in the p-block of the PeriodicTable?

A 4, 8

B 6, 12

C 8, 16

D 10, 20(Total 1 mark)

24

41. The electronic structure of an atom of an element in Group 6 of the Periodic Table could be

A 1s2 2s2 2p2

B 1s2 2s2 2p4

C 1s2 2s2 2p6 3s2 3p6 3d6 4s2

D 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6

(Total 1 mark)

42. The electronic configurations of the atoms of four different elements are given below. For whichelement would you expect the value of the first ionization energy to be the largest?

A 1s1

B 1s2

C 1s2 2s1

D 1s2 2s2

(Total 1 mark)

43. Which of the following has the smallest ionic radius?

A F–

B Na+

C Mg2+

D O2–

(Total 1 mark)

25

44. Which of the following does not have exactly 10 electrons?

A An ion of fluorine, F–

B A molecule of methane, CH4

C A molecule of nitrogen, N2

D An ion of sodium, Na+

(Total 1 mark)

26

45. The Born-Haber cycle for the formation of sodium chloride from sodium and chlorine may be represented by a series of steps labelled A to F as shown.

27

(a) (i) Complete the table below by adding the letters A to F next to the corresponding energy changes.

Energy change Letter ΔH

/kJ mol–1

Lattice energy for sodium chloride –775

Enthalpy change of atomization of sodium +109

Enthalpy change of atomization of chlorine +121

First ionization energy of sodium +494

First electron affinity of chlorine

Enthalpy change of formation of sodium chloride –411(3)

(ii) Calculate the first electron affinity of chlorine, in kJ mol–1, from the data given.(2)

28

(b) Lattice energies can be calculated from electrostatic theory (theoretical values) as well as by Born-Haber cycles (experimental values).

Compound Experimental lattice energy

/ kJ mol–1Theoretical lattice energy

/ kJ mol–1

NaCl –770 –766

Agl –889 –778

(i) Comment on the fact that there is close agreement between the values for sodium chloride, NaCl.

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(ii) Explain, in terms of chemical bonding, why the experimental value for silver iodide, AgI, is more exothermic than the value calculated theoretically for the samecompound.

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(c) Suggest why the first ionization energies of the Group 1 elements decrease down the group.

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(Total 10 marks)

30

46. The graph shows the variation in melting temperatures of the elements across Period 3 (Na to Ar) of the Periodic Table.

(a) Complete the table below to show the type of structure and bonding for the elements shown.

Element Structure Bonding

sodium

silicon

sulfur(3)

31

(b) Explain why silicon has a much higher melting temperature than sulfur.

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(c) Explain why the melting temperature increases from sodium to aluminium.

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(d) Magnesium forms the basic oxide magnesium oxide, MgO. This oxide is almost insolublein water. On gentle warming with dilute sulfuric acid, magnesium oxide reacts to form aqueous magnesium sulfate solution.

(i) Describe how you would use the above reaction to prepare a pure sample of magnesium sulfate.

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(ii) Suggest what action should be taken if a pupil spilt a small quantity of dilute sulfuric acid on a laboratory bench.

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(e) The data in the table below will be useful when answering this question.

Soluble in water Insoluble in water

MgSO4 MgCO3

SrCO3

SrSO4

Magnesium carbonate reacts with dilute sulfuric acid.

MgCO3(s) + H2SO4(aq) → MgSO4(aq) + CO2(g) + H2O(l)

(i) Explain why the reaction between strontium carbonate and dilute sulfuric acid stops after a few seconds.

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(ii) Strontium sulfate is produced when aqueous sodium sulfate is added to aqueous strontium chloride.

Give the ionic equation for the reaction, including state symbols.(2)

(Total 16 marks)

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47. Which of these carbon structures is represented by the diagram below?

A Graphite

B Diamond

C A fullerene

D A carbon nanotube(Total 1 mark)

48. Which of these bond angles is the smallest?

A HNH in NH3

B HCH in CH4

C HOH in H2O

D OCO in CO2(Total 1 mark)

35

49. Which statement best describes the shape and bond angles in the molecule SF6?

A Octahedral, 90° and 180°

B Trigonal bipyramidal, 90° and 180°

C Octahedral, 90° and 120°

D Trigonal bipyramidal, 90° and 120°(Total 1 mark)

50. The bonding in gaseous hydrogen halides is best described as

A mainly covalent with an increasing tendency towards ionic as you go down the group.

B mainly covalent with an increasing tendency towards ionic as you go up the group.

C mainly ionic with an increasing tendency towards covalent as you go down the group.

D mainly ionic with an increasing tendency towards covalent as you go up the group.(Total 1 mark)

51. An electric field can affect the direction of a stream of some liquids. Which of these liquids would be affected by an electric field?

A 1-chloropropane

B Pentane

C Tetrachloromethane

D Cyclopentane(Total 1 mark)

36

52. The graph below shows the boiling temperatures of the hydrides of Group 7.

37

(a) (i) Identify the type of intermolecular force that gives rise to the unusually high boiling temperature of hydrogen fluoride.

...........................................................................................................................(1)

(ii) State and explain whether the electronegativity of fluorine is greater than, similar to or less than, that of bromine.

Hence explain why hydrogen fluoride can form the type of intermolecular force named in (a)(i) but hydrogen bromide cannot.

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(iii) Use the graph to predict what the boiling temperature of hydrogen fluoride would be without the presence of the type of intermolecular force named in (a)(i).

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38

(b) Propanone, CH3COCH3, is a useful solvent for cleaning glassware in laboratories.

(i) Why is propanone able to dissolve a wide range of substances?

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(ii) Propanone can be used to remove both water and octane from glassware. For each of these substances, identify the strongest intermolecular force formed with propanone and the feature of the propanone molecule involved.

Water................................................................................................................

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Octane...............................................................................................................

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(Total 8 marks)

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53. Calcium oxide, known as quicklime, is produced by the thermal decomposition of calcium carbonate, found naturally in limestone.

(a) (i) Explain what is meant by the term thermal decomposition.

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(ii) Write an equation for the thermal decomposition of calcium carbonate, including state symbols.

(1)

(iii) Other Group 2 carbonates can also undergo thermal decomposition. Describe and explain the trend in thermal stability of carbonates down Group 2.

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40

(b) 0.121 g of an impure sample of quicklime was dissolved in 50.0 cm3 of hydrochloric

acid, concentration 0.100 mol dm–3. The excess hydrochloric acid was titrated with

sodium hydroxide solution, concentration 0.100 mol dm–3, and 18.0 cm3 was needed to just neutralize the acid. The indicator used was methyl orange.

The equations for the reactions involved are shown below.

CaO(s) + 2HCl(aq) → CaCl2(aq) + H2O(l)

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

(i) What colour would the indicator be at the end-point?

...........................................................................................................................(1)

(ii) Calculate the number of moles of hydrochloric acid that reacted with the sodium hydroxide solution.

(1)

(iii) Calculate the number of moles of hydrochloric acid originally added to the quicklime. Use this answer and your answer to (b)(ii) to calculate the number of moles of quicklime that reacted with the hydrochloric acid.

(2)

(iv) Calculate the percentage purity of the sample of quicklime. Give your answer to three significant figures.

(2)

41

(c) (i) Describe how to carry out a flame test on the impure sample of quicklime to confirm that it contains calcium ions.

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(ii) If the flame test gave a green colour, in addition to the expected brick red flame, which Group 2 metal is also likely to be present?

...........................................................................................................................(1)

(Total 16 marks)

54. Which of the following graphs shows the variation in the ionic radius of the Group 2 elements?

(Total 1 mark)

42

55. The first five ionization energies of an element, Z, are:

790, 1600, 3200, 4400, 16100 kJ mol–1

In which group of the Periodic Table is Z found?

A 2

B 3

C 4

D 5(Total 1 mark)

56. Which of the following contains the greatest number of hydrogen atoms?

A 2 moles of water, H2O

B 1.5 moles of ammonia, NH3

C 1 mole of hydrogen gas, H2

D 0.5 moles of methane, CH4(Total 1 mark)

57. In a molecule of ethene, C2H4, how many π (pi) bonds are present?

A One

B Two

C Three

D Four(Total 1 mark)

43

58. (a) (i) Complete the electronic configuration of the magnesium atom.

1s2......................................................................................................................(1)

(ii) Complete the electronic configuration of the chlorine atom.

1s2......................................................................................................................(1)

(b) (i) Write the equation, including state symbols, for the reaction of magnesium with chlorine.

(2)

(ii) Name the type of bonding present in magnesium chloride.

...........................................................................................................................(1)

(iii) Draw a diagram (using dots or crosses) to show the bonding in magnesium chloride. Include ALL the electrons in each species and the charges present.

(3)

(c) State the type of bonding that exists in solid magnesium.

Type.............................................................................................................................(1)

44

(d) Explain fully why the melting temperature of magnesium is higher than that of sodium.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 12 marks)

59. (a) Define the term first ionization energy.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(b) Write an equation, with state symbols, to illustrate the process occurring when the secondionization energy of sodium is measured.

(2)

45

(c) The graph below shows the variation in the first ionization energies of some of the elements in Period 3.

First ionization

energy/kJ mol–1

46

(i) On the graph, use crosses to show the approximate values of the first ionization energies for the elements Na, P and S.

Join the crosses to complete your graph.(3)

(ii) Explain why the first ionization energies generally increase across the period sodium to argon (Na to Ar).

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(iii) Explain why the first ionization energy of aluminium is less than that of magnesium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

47

(d) Place the following species

S+ S S–

in order of increasing first ionization energy, starting with the lowest.

Lowest first Highest first

ionization energy ionization energy

................................ ................................ ................................(1)

(Total 14 marks)

60. (a) Define the term covalent bond.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Nitrogen forms an oxide called nitrous oxide, N2O. The bonding in nitrous oxide can be represented as:

N N → O

Complete the diagram below for the N2O molecule using dots or crosses to represent electrons. Just show all of the outer shell electrons.

(3)(Total 5 marks)

48

61. Which of these four molecules, PCl3, CO, CO2 and CCl4, are polar?

A All four

B PCl3 and CO

C CO and CCl4

D PCl3 and CO2(Total 1 mark)

62. Which intermolecular forces exist between molecules of ethoxyethane?

A Instantaneous dipole – induced dipole only

B Permanent dipole – permanent dipole only

C Instantaneous dipole – induced dipole and hydrogen bonds

D Instantaneous dipole – induced dipole and permanent dipole – permanent dipole(Total 1 mark)

63. The following liquids all have the same number of electrons in each molecule. Which one is likely to have the lowest boiling point?

A CH3CH2CH2CH2OH

B CH3CH2CH2CH2CH3

C CH3C(CH3)2CH3

D CH3CH(CH3)CH2CH3(Total 1 mark)

49

64. Which of these is likely to be the best solvent for cyclohexanol?

A H2O(l)

B CH3COCH3(l)

C NaCl(aq)

D CH3CH2CH2CH2CH2CH3(l)(Total 1 mark)

65. The ability of a liquid to flow is linked to the strength of its intermolecular forces.Suggest whichof these liquids flows the slowest when poured.

A Propane-1,2,3-triol

B Propane-1,2-diol

C Pentane

D Butane(Total 1 mark)

66. This question is about boron and nitrogen compounds.

(a) Draw and name the shape of a boron trifluoride, BF3, molecule. Suggest the FBF bond angle.

Name of shape

.....................................................................................................................................

FBF bond angle

.....................................................................................................................................(3)

50

(b) Ammonia has the formula NH3. Its HNH bond angle is less than the FBF bond angle in boron trifluoride.

(i) Estimate the HNH bond angle in NH3.

...........................................................................................................................(1)

(ii) Explain why the HNH bond angle is less than that for FBF.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(iii) Name the strongest intermolecular force between BF3 molecules.

...........................................................................................................................(1)

(iv) Name the strongest intermolecular force between NH3 molecules.

...........................................................................................................................(1)

51

(c) Ammonia will react with oxygen in the presence of a platinum catalyst at 750°C forming water and nitrogen(II) oxide, NO.

(i) What is the oxidation number of nitrogen in ammonia, NH3?

...........................................................................................................................(1)

(ii) The diagram below shows the distribution of molecular energies in the reaction at 750°C. On the same diagram, draw a curve to show the distribution at 500°C and explain what effect this change in temperature would have on the rate of the reaction.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

52

(d) Explain how a catalyst speeds up the rate of a reaction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 14 marks)

67. Going across a period in the Periodic Table from left to right, the general trend is that

A the bonding in the element itself changes from ionic to covalent

B the number of neutrons in the nucleus increases

C the first ionisation energy decreases

D the metallic character increases(Total 1 mark)

68. The electron configurations of argon, iron, chlorine and one other element are given below, but not in order. Which one represents the unnamed element?

A 1s2 2s2 2p6 3s2 3p6 3d6 4s2

B 1s2 2s2 2p6 3s2 3p6

C 1s2 2s2 2p6 3s2 3p4

D 1s2 2s2 2p6 3s2 3p5

(Total 1 mark)

53

69. Which of the following equations represents the first ionisation of sulfur?

A S(s) + e– S–(g)

B S(g) + e– S–(g)

C S(s) S+(g) + e–

D S(g) S+(g) + e–

(Total 1 mark)

70. Which element marked on this graph is a halogen?

Fir

st I

onis

atio

n E

nerg

y

A

B

C

D

A t o m i c n u m b e r ( i n c r e a s i n g i n s t e p s o f o n e )

A

B

C

D(Total 1 mark)

54

71. This question is about the following ionisation energy sequences.

The values are all in kJ mol–1.

A 1400 1000 950 830 700

B 420 3100 4400 5900 8000

C 1000 1250 1520 420 590

D 1520 2700 3900 5800 7200

Select from A to D the sequence which is most likely to represent the following:

(a) The first ionisation energies of five consecutive members of the same group in the Periodic Table, in order of increasing atomic number.

A

B

C

D(1)

(b) The first five ionisation energies of an s-block element.

A

B

C

D(1)

55

(c) The first five ionisation energies of a noble gas.

A

B

C

D(1)

(Total 3 marks)

72. The following data can be used in a Born-Haber cycle for copper(II) bromide, CuBr2.

Enthalpy change of atomisation of bromine Hοat[½Br2(l)] +111.9 kJ mol–1

Enthalpy change of atomisation of copper, Hοat[Cu(s)] +338.3 kJ mol–1

First ionisation energy of copper, Em1[Cu(g)] +746.0 kJ mol–1

Second ionisation energy of copper, Em2 [Cu(g)] +1958.0 kJ mol–1

Electron affinity of bromine, Eaff[Br(g)] –342.6 kJ mol–1

Enthalpy change of formation of CuBr2(s), Hοf [CuBr2(s)] –141.8 kJ mol–1

(a) On the following outline of a Born-Haber cycle complete the boxes A, B, and C by putting in the formula and state symbol for the appropriate species and writing the name of the enthalpy change D.

C u ( g ) C u B r2 +2 ( s )2 B r ( g )–

C u ( s ) + B r 2 ( l )

B

A

C D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+

(3)

56

(b) Use the data to calculate a value for the lattice energy of copper(II) bromide.

Give a sign and units in your answer.

(3)

(c) When the lattice energy of copper(II) bromide is calculated from ionic radii and charges, the result is a value numerically about 10% less than the one obtained from the Born-Haber cycle.

(i) What does this suggest about the nature of the bonding in copper(II) bromide?

...........................................................................................................................

...........................................................................................................................(1)

(ii) Draw a diagram to show how the smaller copper ion alters the shape of the larger bromide ion.

(1)(Total 8 marks)

57

73. Which of the following best describes the molecular shape of carbon dioxide, CO2?

A linear

B trigonal planar

C triangular

D v-shaped(Total 1 mark)

74. Which of the following species is polar?

A NH3

B BF3

C SO3

D CO3(Total 1 mark)

75. Polar liquids are affected by electric fields. For which of the following liquids would a jet of theliquid be affected by an electric field?

A hexane

B cyclohexane

C cyclohexene

D cyclohexanol(Total 1 mark)

58

76. What are the intermolecular forces in methanal, HCHO?

A London forces only

B hydrogen bonds and London forces

C permanent dipole – permanent dipole only

D permanent dipole – permanent dipole and London forces(Total 1 mark)

77. Which of the following substances is likely to be insoluble in water?

A methanol, CH3OH

B ethanol, CH3CH2OH

C fluoromethane, CH3F

D hydrogen fluoride, HF(Total 1 mark)

78. The following liquids have a similar number of electrons per molecule. Suggest which is likely to have the highest boiling point?

A CH3CH2CH2CH2CH3

B (CH3)3COH

C CH3CH2CH(OH)CH3

D CH3CH2CH2CH2OH(Total 1 mark)

59

79. The Group 2 metals, considered in order of increasing atomic number, show a decrease in

A first ionisation energy

B nuclear charge

C chemical reactivity

D ionic radius(Total 1 mark)

80. (a) (i) Name the type of bonding that exists between water molecules.

...........................................................................................................................(1)

(ii) Draw a diagram to show this bonding. Use displayed formulae of two water molecules. Clearly mark and label the bond angle between the water molecules.

(2)

(b) (i) Draw the boron trichloride molecule, BCl3, making its shape clear. Mark the bond angle on your diagram.

(2)

60

(ii) Explain why boron trichloride has this shape.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(iii) Explain why a B–Cl bond is polar.

...........................................................................................................................

...........................................................................................................................(1)

(iv) Explain why a BCl3 molecule is non-polar.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(v) Name the strongest intermolecular force between boron trichloride molecules.

...........................................................................................................................(1)

(Total 11 marks)

61

81. Two compounds may be similar in that they both have

A dative covalent bonds in their molecules

B at least one bond angle of 120° in each molecule

C non-polar molecules

D linear molecules

Select from A–D, the similarity between each of the compounds below.

(a) Benzene, C6H6 and cyclohexane, C6H12

A

B

C

D(1)

(b) Hydrogen cyanide, HCN, and carbon dioxide, CO2

A

B

C

D(1)

(Total 2 marks)

62

82. Select, from A–D, the type of interaction which best describes the bonding between

(a) adjacent polymer chains in [–CH2–CH2–]n

A dative covalent

B London forces

C ion-dipole

D ionic(1)

(b) copper ions and ammonia in Cu(NH3)42+

A dative covalent

B London forces

C ion-dipole

D ionic(1)

(Total 2 marks)

83. (a) A sample of an element can be analysed to show its isotopic composition using a mass spectrometer.

(i) Explain how the sample is ionised.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) State the TWO properties of the ion that determine the path of the ion through the magnetic field.

...........................................................................................................................

...........................................................................................................................(2)

63

(b) Define relative isotopic mass.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) The following data were obtained from the mass spectrum of a sample of chromium.

Relative isotopic mass Percentage abundance

49.95 4.345

51.94 83.79

52.94 9.501

53.94 2.364

Calculate the relative atomic mass of this sample of chromium.

Give your answer to four significant figures.

(2)

(d) Complete the electron configuration of an iron atom, atomic number 26.

1s 2s 2p 3s 3p 3d 4s

↑↓ ↑↓ ↑↓ ↑↓ ↑↓(2)

(Total 10 marks)

64

84. (a) The graph below shows the first ionisation energies of the elements Li, Be, and B.

Complete the graph by adding the approximate first ionisation energies of the elements C to Ne.

E n e r g y

L i B e B C N O F N e

E l e m e n t s

F i r s t i o n i s a t i o n e n e r g y o f t h e e l e m e n t s L i t o N e

(2)

65

(b) Explain why the general trend is for the first ionisation energy to increase across the period.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) Explain why the first ionisation energy of boron, B, is lower than that of beryllium, Be.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 7 marks)

66

85. The data below shows the decomposition temperatures of the carbonates of two Group 2 elements.

Compound Decompositiontemperature / °C

MgCO3 400

BaCO3 1360

Use the idea of polarisation of ions to explain why MgCO3 decomposes more readily than BaCO3.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(Total 3 marks)

67

86. Phosphorus reacts with a limited amount of chlorine to produce phosphorus trichloride, PCl3.

(i) Draw a dot and cross diagram to show the arrangement of the electrons in phosphorus trichloride, PCl3. You need only show the outer shell electrons.

(2)

(ii) Draw the phosphorus trichloride molecule, making its three-dimensional shape clear.

(1)

68

(iii) Explain

• the shape of the phosphorus trichloride molecule.

• why the Cl P Cl bond angle is different from the H C H bond angle in methane, CH4.

...........................................................................................................................

...........................................................................................................................

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...........................................................................................................................(3)

(Total 6 marks)

69

87. (i) Draw the shape of a water molecule. Justify your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(ii) Water has intermolecular hydrogen bonds, but hydrogen sulphide, H2S, does not.

Explain how these arise in water and why they do not occur in hydrogen sulphide.

Give ONE resulting difference in physical properties of water and hydrogen sulphide.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 5 marks)

70

88. A sample of the element osmium, atomic number 76, is made up of four isotopes. The sample has the following percentage composition.

Relative AtomicMass of Isotope

% Composition

188 15.20

189 17.40

190 26.40

192 41.00

(i) What is the minimum number of neutrons present in any single atom of osmium in the sample?

.....................................................................................................................................(1)

(ii) Calculate the average relative atomic mass of osmium in the sample. Give your answer tofour significant figures.

(2)(Total 3 marks)

71

89. (a) The diagram shows the type of bonding present in the elements lithium and sodium in thesolid state.

+ + +

+ +

+ + +

D e l o c a l i s e d e l e c t r o n s

I o n s

(i) What name is given to this type of bonding?

...........................................................................................................................(1)

(ii) Suggest why the melting point of lithium is greater than that of sodium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(b) Lithium can react with chlorine to produce lithium chloride. When a sample of lithium chloride is heated in a Bunsen flame, a red colour is seen.

(i) Draw a ‘dot and cross’ diagram of lithium chloride showing all the electrons.Indicate the charges clearly on your diagram.

(2)

72

(ii) Describe the changes that occur within the lithium ion to produce the flame colour.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Name ONE other metallic element whose compounds produce a red coloured flame.

...........................................................................................................................(1)

(Total 8 marks)

90. This question is about three organic compounds with the following physical properties:

Compound Formula Boiling Point /KΔHο

vap

/ kJ mol–1

Butane CH3CH2CH2CH3 273 6.9

Propan-1-ol CH3CH2CH2OH 371 14.8

Propanone CH3COCH3 330 9.0

(a) (i) Name the intermolecular force present in all three compounds.

...........................................................................................................................(1)

(ii) Explain why this intermolecular force is likely to have a similar strength in butane and propan-1-ol.

...........................................................................................................................

...........................................................................................................................(1)

73

(b) (i) Draw a ‘dot and cross’ diagram for the propan-1-ol molecule, showing outer electrons only.

(1)

(ii) Name the strong additional intermolecular force between propan-1-ol molecules not present in the other two compounds.

...........................................................................................................................(1)

(iii) Using displayed formulae, draw a diagram to show this intermolecular force between two propan-1-ol molecules.

State the values of the following bond angles:

COH ..................

The bond angle between the molecules ..................(3)

(c) (i) Name the intermolecular force between propanone molecules that is not present in butane.

...........................................................................................................................(1)

74

(ii) Explain why you would expect propanone to mix with propan-1-ol.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 10 marks)

91. (a) Complete the electronic configuration of a copper atom and a bromide ion.

(i) Copper atom, Cu 1s22s22p63s23p6 ..............................................................(1)

(ii) Bromide ion, Br– 1s22s22p63s23p6 ..............................................................(1)

(b) Define the term relative atomic mass.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

75

(c) The following data were obtained for a mass spectrum of a sample of copper.

Relative isotopic mass Percentage abundance

62.93 69.17

64.93 30.83

Calculate the relative atomic mass of this sample of copper. Give your answer to two decimal places.

(2)

(d) Copper occurs naturally as the mineral malachite. The composition, by mass, of malachiteis as follows:

Cu = 57.5% C = 5.4% O = 36.2% H = 0.9%

(i) Calculate its empirical formula.

(2)

76

(ii) The molar mass of malachite is 221 g mol–1. Calculate its formula.

(1)

(e) Copper forms a chloride, CuCl2. Use the data below to calculate the maximum and the minimum values for the molar mass of CuCl2.

Data : Relative isotopic masses of chlorine are 35 and 37.Relative isotopic masses of copper are 63 and 65.

(2)(Total 11 marks)

92. Beryllium chloride, BeCl2, is covalent.

(i) Use ideas of ion polarisation or electronegativity to suggest why beryllium chloride, a compound of a metal and a non-metal, is covalent rather than ionic.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

77

(ii) Draw a ‘dot and cross’ diagram to show the bonding in a beryllium chloride molecule, BeCl2. In your diagram show all the outer shell electrons in the atoms of beryllium and chlorine.

(1)(Total 3 marks)

93. In hydrogen fluoride, HF, and water, H2O, the major intermolecular force is the hydrogen bond.

(a) Draw a diagram to show the formation of hydrogen bonds between water molecules in ice. Show at least three water molecules in your diagram and any relevant polarity in the molecules.

(3)

78

(b) Suggest why water has a higher boiling temperature than hydrogen fluoride.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) When hydrogen fluoride reacts with water it forms hydrogen ions. A lone pair of

electrons on the water molecule joins with the hydrogen ion, H+, to produce the ion H3O+.

(i) Draw a diagram to show clearly the shape of the H3O+ ion.

(1)

(ii) Suggest an approximate value for the bond angle H—O—H in H3O+.

...........................................................................................................................(1)

79

(iii) The oxygen atom in water has two lone pairs of electrons. Suggest why the ion

H4O2+ is not generally formed in acid solutions that contain the H+ ion.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(Total 8 marks)

94. (a) Cooking fuels and petrol for car engines need to be gases or liquids which vaporise easily.This will be the case if the intermolecular forces are weak.

Two common fuels are methane, CH4, and 2,2,4-trimethylpentane, C8H18.

Electronegativity

carbon 2.1

hydrogen 2.5

(i) Explain the meaning of the term electronegativity.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

80

(ii) The C—H bond in methane has some polarity but overall the molecule is non-polar.

Explain why methane is a non-polar molecule.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Identify the strongest intermolecular force that exists between2,2,4-trimethylpentane molecules in the liquid state.

...........................................................................................................................(1)

(b) In a car engine 2,2,4-trimethylpentane burns in air to produce carbon dioxide and water.

The equation is

2C8H18 + 25O2 → 16CO2 + 18H2O

Molar mass of C8H18 = 114 g mol–1

(i) Calculate the volume of oxygen needed to burn 700 g of 2,2,4-trimethylpentane.

[Assume the molar volume of a gas = 24.0 dm3 mol–1]

(3)

81

(ii) Calculate the mass of carbon dioxide produced in the reaction in (i).

(2)(Total 10 marks)

95. First ionisation energy and melting temperature are periodic properties shown by elements.

(a) Define the term first ionisation energy.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(b) Explain why the first ionisation energy of potassium is less than that of sodium.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

82

(c) The table shows the melting temperatures of the elements of period 3.

Na Mg Al Si P(white)

S Cl Ar

Melting temperature/K

371 923 933 1683 317 392 172 84

Type of structure

(i) Complete the table to suggest the type of structure shown by the elements.Choose your answers from the following list:

giant atomic structure: metallic structure: simple molecular.(1)

(ii) Explain why silicon has a very high melting temperature.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Explain why aluminium has a higher melting temperature than sodium.

...........................................................................................................................

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...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 11 marks)

83

96. (a) Draw the displayed formula of a branched chain ketone containing five carbon atoms.

(2)

(b) Give the systematic name for this ketone.

.....................................................................................................................................(1)

(c) What is the molecular formula of the alcohol this ketone could be made from?

.....................................................................................................................................(1)

(d) An alcohol can be converted into a ketone by oxidation with sodium dichromate(VI) and sulphuric acid.

Explain why refluxing the mixture first, rather than immediately distilling the product over from the beginning, results in a higher yield of the ketone.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 5 marks)

84

97. The diagram below shows the arrangement of electrons in the energy levels of a sodium atom.

n =

n = 4

n = 3

n = 2

n = 1

(i) Why are the two electrons shown in the n = 1 energy level represented by arrows pointingin opposite directions?

.....................................................................................................................................

.....................................................................................................................................(1)

(ii) Draw an arrow on the diagram to represent the energy change when a sodium atom ionises by losing an electron.

(2)

(iii) Do all of the electrons in the n = 2 energy level have the same energy? Explain your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

85

(iv) How would the arrangement of electrons in a potassium atom differ from this arrangement of electrons in sodium?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 6 marks)

86

98. Silicon, phosphorus and sulphur form chlorides with molecular formulae SiCl4, PCl3, SCl2.

Draw the shapes you would expect for these molecules, suggesting a value for the bond angle ineach case.

SiCl4

ClSiCl bond angle ...............

PCl3

ClPCl bond angle ...............

SCl2

ClSCl bond angle ...............(Total 3 marks)

87

99. (a) Complete the table below which is about the isotopes and an ion of bromine.

Number of

protons neutrons electrons

Br7935 35 35

Br8135 46 35

Br8135 35 46

(3)

(b) Complete the electronic configurations of

Na 1s2 ..........................................................................................................................

Br 1s2 ...........................................................................................................................(2)

(c) Explain why the isotopes of bromine have identical chemical reactions.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(d) What instrument could be used to measure the abundance and mass of the isotopes of bromine?

.....................................................................................................................................(1)

88

(e) The isotopic abundance of bromine is shown below.

Relative isotopic mass Percentage abundance

78.93 50.54

80.91 49.46

Calculate the relative atomic mass of bromine. Give your answer to four significant figures.

(2)

(f) State the types of bonding present in bromine liquid

between the atoms .......................................................................................................

between the molecules ................................................................................................(2)

(Total 11 marks)

89

100. State the type of bond that exists in sodium bromide.

Draw a dot and cross diagram of sodium bromide, showing only the outer shell electrons.

Type .......................................................................................................................................

Dot and cross diagram

(Total 3 marks)

101. (a) (i) Define the term first ionisation energy.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(ii) Write the equation for the process occurring when the second ionisation energy of oxygen is measured.

...........................................................................................................................(1)

90

(b) The graph below shows the first seven successive ionisation energies of an element, X, which is in Period 3 of the Periodic Table.

3 0 0 0 0

2 5 0 0 0

2 0 0 0 0

1 5 0 0 0

1 0 0 0 0

5 0 0 0

00 1 2 3 4 5 6 7

N u m b e r o f t h e e l e c t r o n r e m o v e d

I o n i s a t i o ne n e r g y/ k J m o l – 1

(i) Use the information on the graph to state in which Group of the Periodic Table X is found. Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) Identify the element X.

...........................................................................................................................(1)

(c) The mass spectrum of X shows a singly charged molecular ion at m/e = 256.

Write the formula of this ion.

.....................................................................................................................................(2)

(Total 9 marks)

91

102. Draw a ‘dot and cross’ diagram to show the ions in calcium oxide. Include ALL the electrons and charges.

(Total 2 marks)

103. (a) Fill in the table below to show the number of protons and electrons present in a hydride

ion, H–, and a lithium ion, Li+.

Use the Periodic Table as a source of data.

Protons Electrons

H–

Li+

(2)

(b) Which of these ions is larger, H– or Li+?

Use the numbers you have entered in the table above to explain your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 4 marks)

92

104. Some of the ionisation energies of four elements, Q, R, S and T, with consecutive atomic numbers, are shown in the table below.

Ionisation Energies / kJ mol–1

1st 2nd 3rd 4th 5th

Q 2081 3952 6122 9370 12177

R 496 4563 6913 9544 13352

S 738 1451 10541 13629

T

(a) To which group of the Periodic Table does R belong? Give a reason for your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Estimate values, in kJ mol–1, for the third ionisation energy of S, and the first ionisation energy of T, represented by the shaded gaps shown in the table above.

S ..........................

T ..........................(2)

(c) Which element is least likely to form compounds? Give a reason for your answer.

.....................................................................................................................................

.....................................................................................................................................(1)

93

(d) Write a balanced equation which represents the change that corresponds to the third ionisation energy of R.

Use R as the symbol for the element and include state symbols in your answer.

(2)

(e) Element X is in the same group of the Periodic Table as R, but is immediately below it.

The first ionisation energy of X is 419 kJ mol–1. Explain why this value is lower for X than for R.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 8 marks)

105. A methanol molecule has 18 electrons in total.

(i) Give the name and formula of a hydrocarbon with the same number of electrons.

Name ............................................

Formula

(1)

94

(ii) Which intermolecular force depends to a large extent on the number of electrons present?

.....................................................................................................................................(1)

(iii) Would you expect methanol or your hydrocarbon in (i) to have the higher boiling point? Justify your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(iv) Draw a diagram to show the strongest intermolecular force between TWO molecules of the compound with the higher boiling point.Indicate and give the value of the bond angle between these two molecules.

.....................................................................................................................................(2)

(Total 5 marks)

106. (a) Complete the table below which is about isotopes and an ion of magnesium.

Numbers of

Protons Neutrons Electrons

Mg2412 12 12

Mg2612 12 12

22412 Mg 12 12

(3)

95

(b) Complete the electronic configurations of magnesium and chlorine atoms.

1s 2s 2p 3s 3p

Mg ↓↑ ↓↑

(1)

1s 2s 2p 3s 3p

Cl ↓↑ ↓↑

(1)

(c) Write the equation, including state symbols, for the reaction of magnesium with chlorine.

.....................................................................................................................................(2)

(d) The mass spectrum of a sample of chlorine molecules shows three molecular peaks.These are formed from the molecules shown below.

Molecule Percentage abundance

35Cl-35Cl 56.25

35Cl-37Cl 37.50

37Cl-37Cl 6.25

Calculate the relative molecular mass of chlorine in this sample.

(2)

96

(e) Calculate the volume of 4.73 g of chlorine gas at 100 °C.

[The molar volume of a gas at 100 °C = 30.6 dm3 mol–1]

(2)

(f) State and explain the type of bond that exists in solid magnesium.

Type ..............................................................

Explanation ................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(g) State the type of bond that exists in magnesium chloride. Draw a dot and cross diagram showing the outer shell electrons.

Type ..............................................................

Dot and cross diagram

(3)(Total 17 marks)

97

107. (a) Define the term

(i) atomic number

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(ii) mass number

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(b) First ionisation energies of the elements show periodicity. The graph below shows the first ionisation energy of twelve successive elements in the Periodic Table in order of increasing atomic number.The letters are not the symbols for the elements.

A B C D E F G H J K L M

E l e m e n t

F i r s tI o n i s a t i o nE n e r g y

A

B

C

D

E

F

G

HJ

K

L

M

98

(i) Give the letters of the two elements in Group 0 (the noble gases).

Explain your answer in terms of ionisation energy.

Letters .................... and ....................

Explanation .......................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) Give the letter of the Group 3 element.

Explain your answer in terms of ionisation energy.

Letter ....................

Explanation .......................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Explain why there is an increase in the first ionisation energy of the elements from F to H shown on the graph on the previous page.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 8 marks)

99

108. (a) (i) A diagram of the structure of solid sodium chloride is shown below.

Label the diagram to identify the particles present in solid sodium chloride.

(1)

(ii) Explain why sodium chloride has a high melting temperature.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

100

(b) A diagram of the structure of solid graphite is shown below.

On the diagram name and label the types of bonding that exist in solid graphite.

(2)

(c) A diagram of the structure of solid diamond is shown below.

On the diagram name and label the type of bond that exists in solid diamond.

(1)

101

(d) The densities of diamond and graphite are

Density / g cm–3

Diamond 3.53

Graphite 2.25

Suggest, using information from (b) and (c), why diamond is more dense than graphite.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 8 marks)

109. The graph shows the boiling temperatures of the hydrogen halides, hydrogen fluoride, HF, to hydrogen iodide, HI.

3 1 02 9 0

2 7 0

2 5 0

2 3 0

2 1 0

1 9 0

1 7 0

1 5 0H F H IH B rH C l

b o i l i n gt e m p e r a t u r e / K

h y d r o g e n h a l i d e

102

(a) Complete the table to identify the strongest intermolecular forces present in the liquid form of each hydrogen halide.

Hydrogenhalide

Strongest intermolecular force

HF

HCl

HBr

HI(2)

(b) Explain why HF has a higher boiling temperature than the other hydrogen halides and why there is an increase from HCl to HI.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 5 marks)

110. (a) What is the formula for strontium fluoride?Use the Periodic Table as a source of information.

.....................................................................................................................................(1)

103

(b) Draw a ‘dot and cross’ diagram for the fluoride ion.Include all electrons and the charge on the ion.

(1)(Total 2 marks)

111. A sample of gallium, Ga, (atomic number 31) was found to consist of two different types of atoms with mass numbers 69 and 71. 60.2% of the sample had the lower mass number.

(a) What is the name given to atoms of the same element with different mass numbers?

.....................................................................................................................................(1)

(b) How many neutrons are there in an atom of gallium with mass number 71?

..............................................(1)

(c) (i) What instrument would be used to obtain the percentage composition of the gallium sample?

...........................................................................................................................(1)

(ii) Calculate the average atomic mass of gallium in this sample. Show your working and give your answer to 3 significant figures.

(2)

104

(d) (i) Complete the electron configuration of a gallium atom, using the s p d notation.

1s2 ......................................................................................................................(2)

(ii) Write a balanced equation which represents the change that corresponds to the firstionisation energy of gallium. Include state symbols in your answer.

(2)

(iii) The first four ionisation energies, in kJ mol–1, of the Group 3 elements gallium and indium and the Group 4 elements germanium and tin are shown below.

A 558 1821 2705 5200B 579 1979 2963 6200C 709 1412 2943 3930D 762 1537 3302 4411

Which set of figures, A, B, C or D, represents gallium? ..................................(1)

(Total 10 marks)

112. (a) Complete the electron configuration for carbon.

1s2 ........................................................................(1)

105

(b) Explain how successive ionisation energy data could be used to confirm that carbon is in Group 4 of the Periodic Table.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(c) Draw a dot and cross diagram for a molecule of carbon tetrachloride, CCl4, showing outer electrons only.

(2)

(d) Explain how the following are achieved in a mass spectrometer.

(i) Ionisation

...........................................................................................................................

...........................................................................................................................

(2)

(ii) Deflection

...........................................................................................................................(1)

106

(e) (i) Define the term relative isotopic mass.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(ii) Carbon consists of the isotopes 12C, 13C and 14C. Chlorine consists of the isotopes 35Cl and 37Cl.

Use this data to calculate the maximum relative molecular mass of a molecule of carbon tetrachloride, CCl4.

(1)

(iii) Explain, in terms of sub-atomic particles, the meaning of the term isotopes.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

107

(iv) Why do isotopes of the same element have the same chemical properties?

...........................................................................................................................

...........................................................................................................................(1)

(Total 14 marks)

113. (a) Methane and poly(ethene) are both hydrocarbons.

(i) State the type of bond between carbon and hydrogen atoms in the molecules of both compounds.

.....................................................................................(1)

(ii) State the type of intermolecular force present in both compounds.

.....................................................................................(1)

(iii) Explain why poly(ethene) melts at a higher temperature than methane.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

108

(b) Explain, in terms of its bonding, why magnesium has a high melting temperature.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 7 marks)

114. (a) Sodium iodide reacts with chlorine to produce sodium chloride and iodine.

(i) State the oxidation numbers of the iodine and chlorine species in the spaces provided.

2NaI + Cl2 → 2NaCl + I2

.......... .......... .......... .........(2)

(ii) Use these oxidation numbers to explain why this reaction is a redox reaction.

...........................................................................................................................

...........................................................................................................................(2)

109

(iii) Calculate the maximum mass of iodine that could be produced from 30.0 g of sodium iodide.

(3)

(iv) Calculate the volume of chlorine gas required to produce this amount of iodine.

[1 mol of gas occupies 24 dm3 under the conditions of the experiment]

(1)

(b) (i) Give the colour of iodine and its physical state at room temperature and pressure.

Colour ........................................................................................

Physical state .............................................................................(2)

110

(ii) Write an equation, including state symbols, to represent the process occurring whenthe first ionisation energy of iodine atoms is measured.

...........................................................................................................................(2)

(Total 12 marks)

115. (a) (i) Explain why a water molecule does not have a linear shape.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) State the HOH bond angle in water and explain why it has this value.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(b) (i) Draw the boron trichloride molecule, BCl3, making its shape clear. Mark in the bond angle on your diagram.

(2)

111

(ii) Explain why a B–Cl bond is polar.

...........................................................................................................................

...........................................................................................................................(1)

(iii) Explain why a BCl3 molecule is non-polar.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(iv) Name the strongest intermolecular force between boron trichloride molecules.

...........................................................................................................................

...........................................................................................................................(1)

112

(c) A compound of phosphorus and chlorine has the composition by mass shown below.

Element % by mass

P 14.9

Cl 85.1

Calculate the empirical formula of this compound.

(2)(Total 11 marks)

116. (a) Write an equation for the reaction of calcium with oxygen to form calcium oxide, CaO.

.....................................................................................................................................(1)

113

(b) Draw a ‘dot and cross’ diagram of calcium oxide, CaO, showing all the electrons. Indicate the charges clearly on your diagram.

(2)

(c) (i) Name the compound formed when calcium oxide reacts with water.

...........................................................................................................................(1)

(ii) Which pH or pH range would include the pH of a saturated solution of the product of this reaction?

pH 0–4 5–6 7 8–9 10–14

................................................................(1)

(Total 5 marks)

114

117. (a) The mass of one atom of the isotope Br7935 is 1.31 × 10–22 g. The molar mass of Br79

35 is

79.0 g mol–1.

Use this information to calculate a value for the Avogadro constant. Give your answer to three significant figures.

(2)

(b) According to the Periodic Table, the relative atomic mass of naturally occurring bromine is 80.

What information can you deduce from this about naturally occurring bromine?(No calculation is expected.)

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 3 marks)

115

118. This question is about the chemistry of sodium and magnesium.

(a) Sodium and chlorine react together as shown in the equation.

2Na(s) + Cl2(g) 2NaCl(s)

Is sodium oxidised or reduced in this reaction? Explain your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(b) (i) Sodium chloride and magnesium chloride can be distinguished by carrying out a flame test. State the observation you would make for each.

Sodium chloride .........................................................................................

Magnesium chloride .........................................................................................(2)

(ii) Explain the changes which occur when electrons in sodium produce a flamecolour.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Suggest ONE use for the coloured light produced by sodium.

...........................................................................................................................(1)

(c) Write the electron configuration of a magnesium ion, Mg2+, using s, p notation.

.....................................................................................................................................(1)

116

(d) The table below gives some ionisation energies for sodium and magnesium.

First ionisationenergy /

kJ mol–1

Second ionisationenergy /

kJ mol–1

Sodium 496 4563

Magnesium 738

(i) Write the chemical equation, with state symbols, which corresponds to the first ionisation energy of magnesium.

(2)

(ii) Explain why the first ionisation energy of magnesium is greater than the first ionisation energy of sodium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

117

(iii) Predict a value for the second ionisation energy of magnesium. Explain your choice.

Value ........................................kJ mol–1

Explanation .......................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(e) Which atom has the larger radius, sodium or magnesium? Explain your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 15 marks)

118

119. The Hess cycle below can be used to estimate the enthalpy change of formation, Hf, of the unstable gaseous compound with the formula HOCl(g).

H O C l ( g )

H f

E l e m e n t s i n t h e i r s t a n d a r d s t a t e s

+ 5 8 9 k J m o l – 1

+ 6 6 7 k J m o l – 1

G a s e o u s a t o m s o f t h e e l e m e n t s

(a) (i) Insert formulae, with state symbols, into the appropriate boxes, to show the correct quantities of each element.

(1)

(ii) Use the cycle to calculate a value for the enthalpy change of formation, fH

[HOCl(g)].

(1)

119

(iii) Assuming that the H—O bond energy is +464 kJ mol–1, calculate a value for the O—Cl bond energy.

(1)

120

(b) (i) Draw a ‘dot and cross’ diagram for the HOCl molecule showing outer electrons only.

(2)

(ii) Predict the HOCl bond angle. Justify your answer.

Angle ................................................................................................................

Justification ......................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

121

(c) HOCl(g) can be made from chlorine(I) oxide by the reversible reaction

Cl2O(g) + H2O(g) 2HOCl(g)

What effect, if any, would an increase in pressure have on the proportion of HOCl(g) at equilibrium? Justify your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 9 marks)

120. Two reactions of a chloroalkane, X, are shown below.

Propanol-2-ol 1Reaction Chloroalkane X 2Reaction

CH2=CHCH3propene

(a) The chloroalkane X can be used to make propan-2-ol in Reaction 1.

(i) Name and draw the displayed formula of the chloroalkane X.

Name ...........................................................................................................

Displayed formula

(2)

122

(ii) Reaction 1 is an example of nucleophilic substitution. The nucleophile is the hydroxide ion. Use the diagram below to show how it is able to attack the chloroalkane X.

C C l

(2)

(b) (i) What type of reaction is Reaction 2?

.............................................................................(1)

(ii) Give the reagent and conditions needed for this reaction.

Reagent .............................................................................................................

Conditions .........................................................................................................

...........................................................................................................................(2)

(c) Propan-2-ol has a higher boiling point than both the chloroalkane X and propene.

(i) Name the strongest intermolecular force between propan-2-ol molecules.

...........................................................................(1)

123

(ii) Draw a diagram to show this force between two propan-2-ol molecules. Clearly mark and label the bond angle between the molecules.

(2)

(d) Propene, CH2=CHCH3, can be polymerised forming poly(propene).

(i) Draw a section of the poly(propene) polymer chain formed from two monomer units.

(2)

124

(ii) Explain, in terms of intermolecular forces, why poly(propene) is a solid at room temperature.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 14 marks)

121. (a) This question is about 1,2-diaminoethane, H2NCH2CH2NH2.

(i) Draw a ‘dot and cross’ diagram for 1,2-diaminoethane, showing outer electrons only.

(1)

125

(ii) Suggest values for the NCC and HNC bond angles. For each angle justify your suggestion.

NCC angle

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

HNC angle

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(b) Write an equation for the reaction of 1,2-diaminoethane with excess dilute hydrochloric acid.State symbols are not required.

(2)

(c) A green complex, [Ni(H2NCH2CH2NH2)3]2+, forms when 1,2-diaminoethane reacts with nickel(II) ions. Each 1,2-diaminoethane molecule forms two bonds to a nickel(II) ion.

(i) Give the term which describes a ligand that forms two bonds to a metal ion in a complex.

...........................................................................................................................(1)

126

(ii) Name and describe the bond between 1,2-diaminoethane and the nickel(II) ion.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Suggest the shape of the complex.

...........................................................................................................................(1)

(iv) Write the equation for the formation of this complex from hexaaquanickel(II) ions,2

62O)Ni(H .

(1)

(v) Use your knowledge of entropy to explain why this complex is more stable than the hexaaquanickel(II) ion.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

127

(d) A polyamide forms when 1,2–diaminoethane reacts with hexane-1,6-dioyl dichloride.

Draw a structure for this polymer, showing the repeating unit.

(2)(Total 14 marks)

122. Paracetamol can be manufactured from phenol using the reaction sequence below.

O H

S t e p 1

O H

S t e p 2

O H

S t e p 3

O H

N O N H N H C O C H 322

A B C P a r a c e t a m o l

(a) Give reagents and conditions for Step 1.

.....................................................................................................................................

.....................................................................................................................................(2)

128

(b) State the type of reaction that occurs in Step 2.

.....................................................................................................................................(1)

(c) (i) Give the name of compound C.

...........................................................................................................................(1)

(ii) Suggest a test and its results for the amino group in compound C.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(d) (i) Write a balanced equation for the reaction occurring when paracetamol is boiled with an aqueous solution of sodium hydroxide.

(2)

(ii) Would you expect paracetamol to react with sodium carbonate solution? Justify your answer.

...........................................................................................................................

...........................................................................................................................(1)

129

(e) (i) Suggest which types of intermolecular forces exist between paracetamol molecules.For each type of force give an example of the parts of the molecules involved.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(4)

(ii) Suggest a reason why paracetamol is only sparingly soluble in water.

...........................................................................................................................

...........................................................................................................................(1)

(f) Suggest which bond gives rise to the broadest absorption in the infrared spectrum of paracetamol.State the range of wavenumbers for this absorption.

...........................................................................................................................

...........................................................................................................................(2)

(g) (i) Give the molecular formula of the ion with the highest molecular mass in the mass spectrum of paracetamol.

...........................................................................................................................(1)

130

(ii) Suggest the formulae of the ions responsible for the peaks at mass / charge ratios 43 and 93.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(h) Suggest ONE advantage of using paracetamol, rather than aspirin, as a pain reliever.

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 20 marks)

123. (a) Draw the ammonia molecule, NH3, making its three-dimensional shape clear. Mark in thebond angle on your diagram. Explain why ammonia has this shape and this bond angle.

Diagram

Explanation

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

131

(b) Explain whether ammonia is a polar molecule or not.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) Explain, in terms of the intermolecular forces in both compounds, why ammonia has a higher boiling temperature than phosphine, PH3.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(d) (i) Explain, in terms of electrons, how ammonia can react with hydrogen ions to form

ammonium ions, NH4+.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

132

(ii) State the number of protons and the number of electrons present in an ammonium ion.

number of protons .....................................

number of electrons....................................(2)

(Total 13 marks)

124. (a) Sodium chloride, NaCl, can be made by the reaction of sodium with chlorine.

2Na(s) + Cl2(g) 2NaCl(s)

(i) Calculate the maximum mass of sodium chloride which could be obtained from 92 g of sodium.

(2)

(ii) Calculate the concentration of the solution obtained when this mass of

sodium chloride is dissolved in water and made up to a volume of 10 dm3 with distilled water.

(1)

133

(iii) Calculate the volume of chlorine gas required to react with 92 g of sodium.

[1 mol of gas occupies 24 dm3 under the conditions of the experiment]

(2)

(b) Describe the structure of solid sodium metal and explain why it conducts electricity.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) (i) Define the term first ionisation energy.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

134

(ii) Explain why the first ionisation energy of chlorine is higher than that of sodium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 13 marks)

125. (a) (i) Complete the electron configuration of an aluminium atom.

1s2 .......................................................................................................................(1)

135

(ii) The grid below shows the relative values of the 1st and 2nd ionisation energies of

aluminium. Mark on the grid the relative values that you would expect for the 3rd

and 4th ionisation energies of aluminium.

1 s t 2 n d 3 r d 4 t h

E n e r g y

I o n i s a t i o n E n e r g y(2)

(b) (i) Write the half-equation for the oxidation of aluminium metal to aluminium

ions, Al3+.

...........................................................................................................................(1)

(ii) Write the half-equation for the reduction of oxygen gas to oxide ions, O2–.

...........................................................................................................................(1)

136

(iii) Combine these two half-equations to produce the redox equation for the reaction ofaluminium with oxygen to form aluminium oxide.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(Total 6 marks)

126. (a) Calculate the number of atoms in 3.50 g of lithium.

Use the Periodic Table as a source of data.

[The Avogadro constant, L = 6.02 × 1023 mol–1]

(2)

137

(b) The equation for the reaction of lithium with hydrochloric acid is shown below.

2Li(s) + 2HCl(aq) 2LiCl(aq) + H2(g)

(i) Rewrite this equation as an ionic equation, omitting the spectator ions.

(1)

(ii) Draw a ‘dot and cross’ diagram of lithium chloride showing all the electrons. Indicate charges clearly on your diagram.

(2)

138

(iii) The value of the standard enthalpy change for the reaction, Hο, is –557 kJ mol–1. State TWO of the reaction conditions necessary for this enthalpy change to be standard.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 7 marks)

127. (a) An atom of argon has mass number 40. Complete the table below showing the composition of this argon atom.

Use the Periodic Table as a source of data.

Protons

Electrons

Neutrons

(2)

(b) An atom of potassium has mass number 39. Explain, in terms of atomic structure, why argon comes before potassium in the Periodic Table.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

139

(c) A sample of argon contains a mixture of isotopes as shown below.

Calculate the relative atomic mass of argon in the sample. Give your answer to three significant figures.

Isotopic mass % abundance

36.0 1.34

38.0 0.160

40.0 98.5

(2)

(d) Write the electron configuration of argon in s, p notation.

.....................................................................................................................................(1)

(e) The chart shows the first ionisation energy of some elements in the third period of the Periodic Table.

× ×

××

2 0 0 0

1 5 0 0

1 0 0 0

5 0 0

0P S C l A r K

1 s ti o n i s a t i o ne n e r g y/ k J m o l – 1

(i) Write the chemical equation, with state symbols, which corresponds to the first ionisation energy of argon.

...........................................................................................................................(1)

140

(ii) On the chart, add a cross to show the first ionisation energy of potassium. Justify your choice of the position of the cross.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Explain why there is a small decrease in first ionisation energy going from phosphorus to sulphur.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iv) Explain why there is an increase in first ionisation energy going from sulphur to chlorine.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

141

(f) Suggest why argon is used to fill some types of light bulbs.

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 14 marks)

128. Read the passage on Halothane – the first designer anaesthetic straight through, and then more carefully. Answer the following questions.

HALOTHANE – THE FIRST DESIGNER ANAESTHETIC

Various methods have been used since antiquity to lessen operative pain, including hypnosis, theuse of narcotics prepared from marijuana, stupefying with alcohol or even knocking the patient unconscious with a blow to the jaw.

In 1818, Michael Faraday noted the ability of ether vapour to induce a profound lethargic state. Earlier, Humphry Davy had reported the results of his research on nitrogen(I) oxide, and claimed that it appeared capable of destroying physical pain, and might probably be used with advantage during surgical operations. But neither the application of ether nor of nitrogen(I) oxide was followed up at this time.

Three Americans are generally credited with the introduction of inhalation anaesthesia. In 1842, Dr Crawford Long used ether to render a patient unconscious while he removed a cyst from his neck. In 1844, dentist Horace Wells had one of his own teeth painlessly extracted while under nitrogen(I) oxide anaesthesia and in 1846, William Morton successfully used ether to anaesthetise a patient at his dental practice. The era of truly painless operations had begun. In 1847, James Simpson used chloroform (CHCl3) as an anaesthetic for the first time, and for the remainder of the century chloroform, nitrogen(I) oxide and ether reigned supreme as anaestheticagents.

The use of anaesthetics was not, however, without risk. When they were given in sufficiently large amounts to cause muscle relaxation, the doses were not far removed from those which caused breathing paralysis, and ether caused gastric irritation and post-operative vomiting. Chloroform in large, repeated doses, sometimes caused irreversible liver damage. In the early part of the last century, nitrogen(I) oxide was mainly used for quick operations such as tooth extraction, where its analgesic (pain-killing) action also came in useful. However, for any but the most trivial of operations, ether was the anaesthetic of first choice. That said, a significant number of operations ended in explosions – the flammable ether/air mixture would have been ignited by sparks from switches and other electrical apparatus, and sometimes static discharge from clothing. The search was on for an agent lacking all the undesirable chemical and physiological properties associated with ether and chloroform.

142

In 1928, Thomas Midgley came up with the first of the chlorofluoro compounds (CFCs), dichlorodifluoromethane, which he advocated for use as a heat transfer agent in refrigerators. Several research chemists coincidentally realized that CFCs, being non-flammable, non-toxic and volatile might well prove to be promising anaesthetics too. In the mid-1940s, pharmacologist Benjamin Robbins carried out extensive experiments on 46 potential CFC anaesthetics and concluded that:

the majority of the CFCs produced anaesthesia;

within a group of related compounds, potency increased with increasing boiling point;

the introduction of a bromine atom increased the safety of an anaesthetic and its potency.

Subsequently, a research chemist, Charles Suckling, working in the ICI’s laboratories at Widnes,was guided by three factors to help him choose potential anaesthetics. First was the inertness of fluorine in the C—F bond, especially in the CF3 and CF2 groups. The C—F group also conferred stability to adjacent C—Hal bonds. Thus compounds of the type CF3CHalX2 (X = H or Hal) should have high chemical stability and thus low toxicity. Second, the CFCs that had a C—H bond were safer than the totally halogenated alkanes. Chemists reasoned that the greater polar nature of the former species enabled them to interact electrostatically with ‘brain molecules’ and thus show anaesthetic effects at lower doses compared with the latter group. Finally, potential anaesthetics should be able to produce narcosis ("deep sleep") at the lowest concentrations possible.

Only one compound, halothane, CF3CHBrCl, satisfied all these requirements.

The early 1950s, and the arrival of halothane on the clinical scene, marked the start of an exciting new era in anaesthesia. Whereas ether had several problems associated with its use, halothane was a potent inhalation agent with a smooth, pleasant induction for the patient. Although having no analgesic properties, when used in conjunction with intravenous painkillers and muscle relaxant drugs, halothane provided ideal conditions for a multitude of surgical operations, and rapidly became the agent of choice. But was it too good to be true?

Despite its huge popularity and success in the 1960s, warning bells were beginning to ring aboutthe role of halothane in post-operative liver dysfunction, especially after repeated exposure. In the face of increasing concern, it became evident that the concept of a ‘safe period’ between administrations should be questioned.

143

During the 1980s, the use and popularity of halothane began to wane, while the use of even safer and cheaper fluorinated agents, such as enflurane and isoflurane, increased. By the early 1990s halothane’s use had all but ceased, isoflurane having taken its place.

F C C O C F F C C O C F

F

H

C l

F H F H H

F F C l F

i s o f l u r a n ee n f l u r a n e

[777 words]

Adapted from “Halothane - the first designer anaesthetic” by T. Dronsfield, M. Hill and J. Pring, Education in Chemistry, September 2002

(a) What is the formula of nitrogen(I) oxide?

.....................................................................................................................................(1)

(b) Explain the link between the search for good refrigerants and good anaesthetics.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(c) Explain why it was desirable to choose CFCs with CF2 and CF3 groups as potential anaesthetics.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

144

(d) (i) Suggest why the molecule CF3CH2Cl is more polar than CF3CCl3.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(ii) According to the text, which of these two molecules is likely to be the safer to use as an anaesthetic? Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(e) Give the systematic name for halothane.

.....................................................................................................................................(1)

(f) Estimate the value of the COC bond angle in enflurane.

.....................................................................................................................................(1)

(Total 7 marks)

129. Magnesium burns in oxygen to form magnesium oxide, MgO.

(a) Write the equation for the reaction.

................................................................................................................................(1)

145

(b) Draw a dot and cross diagram of magnesium oxide. Show all the electrons.

(2)

(c) Describe the bonding in magnesium. Explain why it is a good conductor of electricity.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(3)

(Total 6 marks)

130. (a) Complete the electronic configuration for calcium, Ca.

1s2 ..........................................................................................................................(1)

146

(b) (i) Define the term first ionisation energy.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(ii) Explain why the first ionisation energy of calcium is lower than that of magnesium.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(c) A sample of magnesium contains three isotopes of mass numbers 24, 25 and 26.

(i) In terms of sub-atomic particles, state ONE similarity and ONE difference betweenthese isotopes.

Similarity .....................................................................................................

......................................................................................................................

Difference .....................................................................................................

......................................................................................................................(2)

147

(ii) The following data were obtained from the mass spectrum of this sample of magnesium.

Peak at m/e %

24.0 78.6

25.0 10.1

26.0 11.3

Calculate the relative atomic mass of this sample of magnesium. Give your answer to 3 significant figures.

(2)(Total 11 marks)

131. Sodium and chlorine react together in a redox reaction to form sodium chloride, NaCl.

(i) Write the half equation for

the oxidation of sodium, Na

...............................................................................................................................

the reduction of chlorine, Cl2.

...............................................................................................................................(2)

(ii) Write the equation for the reaction of sodium with chlorine.

...............................................................................................................................

...............................................................................................................................(1)

(Total 3 marks)

148

132. Silicon reacts with chlorine to produce silicon tetrachloride, as shown in the following equation

Si(s) + 2Cl2(g) → SiCl4(l)

(a) (i) Calculate the mass of silicon tetrachloride obtained from 10.0 g of silicon.

(3)

(ii) Calculate the minimum volume of chlorine that would be required to react completely with 10.0 g of silicon.

[1 mol of gas occupies 24.0 dm3 under the conditions of the experiment]

(2)

149

(b) Draw a silicon tetrachloride molecule, SiCl4, showing its three-dimensional shape.Name the shape and state the bond angle. Explain why the molecule has this shape.

Diagram

Name of shape .............................................................................................................

Bond angle ..............................................

Explanation of shape

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(5)

(c) (i) Why are silicon-chlorine bonds polar?

......................................................................................................................

......................................................................................................................(1)

150

(ii) Explain why the silicon tetrachloride molecule has no permanent dipole.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 13 marks)

133. (a) (i) Write a balanced equation which represents the change that corresponds to the second ionisation energy of magnesium. Include state symbols in your answer.

(2)

(ii) The graph below shows how the second ionisation energy of six consecutive elements in the Periodic Table, represented by the letters A to F, varies with increasing atomic number.

Which of the elements, A to F, could represent magnesium?

..........................................(1)

151

(b) Draw a ‘dot and cross’ diagram to show the ions in magnesium fluoride.Include all electrons and the charges on the ions.

(2)(Total 5 marks)

134. (a) One of the naturally occurring potassium isotopes is 39K.

(i) Write down the numbers of protons, neutrons and electrons present in an atom of 39K. Use the Periodic Table as a source of data.

protons ...................... electrons ....................

neutrons ....................(2)

(ii) Write down the electronic configuration of a potassium atom using s,p,d notation.

...............................................................................................................................(1)

152

(b) To show that potassium manganate(VII), KMnO4, is ionic, the apparatus below canbe used.

The power supply is connected for about 30 minutes.

(i) Give the formula of the coloured ion present in potassium manganate(VII),KMnO4.

...............................................................................................................................(1)

(ii) What would you expect to see after 30 minutes?

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(1)

153

(iii) The gel was replaced with one containing copper(II) sulphate and the experiment repeated. Describe and explain what would be seen.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(Total 7 marks)

Diagram adapted from Nuffield Advanced Science Chemistry Student’s Book, 4th

Edition, p. 64, Fig. 3.20.

135. This question is about the chemistry of methanol, CH3OH.

(a) (i) Draw a ‘dot and cross’ diagram for methanol, showing outer shell electrons only.

(1)

154

(ii) Textbooks show the displayed formula of methanol as follows

However, this is not a true representation of the shape of the molecule.Explain why the shape of methanol is not as shown above.Label the correct value of ONE bond angle on the displayed formula.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(b) When methanol burns in a poor supply of air, one of the products is carbon monoxide.A ‘dot and cross’ diagram of carbon monoxide is shown below.

(i) Draw the displayed formula for carbon monoxide. Show the TWO types of bond which are present.

(1)

(ii) The length of the bond between carbon and oxygen in methanol is 0.143 nm. Would you expect the length of the bond between carbon and oxygen in carbon monoxide to be longer, the same or shorter than this? Explain your answer.

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

155

(c) The energy of the bond between carbon and oxygen in methanol (the C—O bond) can be calculated from data on enthalpy changes of atomisation.

(i) Write an equation, including state symbols, for the atomisation of one mole of methanol vapour.

(1)

(ii) Use the data below to calculate the energy of the C—O bond in methanol.

standard enthalpy change of atomisation of methanol vapour, ∆Hοat = +2039 kJ mol–1

energy of C—H bond, E(C—H) = +413 kJ mol–1

energy of O—H bond, E(O—H) = +464 kJ mol–1

(2)

156

(iii) Complete a balanced Hess cycle which you can use to calculate the standard

enthalpy change of formation of methanol vapour, Hοf.

You should use the value of the standard enthalpy change of atomisation of

methanol vapour, Hοat, given in (ii) and the data on enthalpy changes given

below. Write the correct numerical data beside the arrows in the cycle.

Equation Enthalpy change of atomization

/kJ mol–1

C(graphite) C(g) +716.7½ O2(g) O(g) +249.2½ H2(g) H(g) +218.0

Use your cycle to calculate the value of Hοf for methanol vapour.

(3)

157

(iv) Methanol is a liquid at room temperature. Would you expect the standard enthalpy change of formation of liquid methanol to be more or less negative than the value you calculated in (iii)? Justify your answer.

................................................................................................................................

................................................................................................................................(1)

(v) Methanol is a liquid at room temperature although alkanes with similar molecular mass are gases.

Draw a diagram to show a bond between two methanol molecules that causes it to be a liquid at room temperature.

Give the value of this bond angle on your diagram.

(2)

(d) Methanol can be manufactured in the following reaction.

CO(g) + 2H2(g) CH3OH(g) ∆Hο = –93.3 kJ mol–1

Decide whether a high or low temperature and a high or low pressure would give the greater proportion of methanol at equilibrium. Justify your choice in each case.

Temperature ..................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

Pressure .........................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(2)

(Total 17 marks)

158

136. (a) The table below gives the boiling points of three organic compounds.

Compound Boiling point/K

chloroethane 285

1-chloropropane 320

2-chloropropane 309

(i) Explain why 1-chloropropane has a higher boiling point than chloroethane.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(ii) Explain why 1-chloropropane has a higher boiling point than its isomer, 2-chloropropane.

................................................................................................................................

................................................................................................................................

................................................................................................................................(1)

(b) Both chloroethane and iodoethane react with aqueous potassium hydroxide solution to form ethanol. The hydroxide ions act as nucleophiles.

(i) What is a nucleophile?

................................................................................................................................

................................................................................................................................

................................................................................................................................(1)

159

(ii) Explain why iodoethane reacts faster than chloroethane with aqueous potassium hydroxide, under the same conditions.

................................................................................................................................

................................................................................................................................(1)

(c) (i) Under what conditions does chloroethane react with potassium hydroxide to form ethene rather than ethanol?

...............................................................................................................................

...............................................................................................................................(1)

(ii) Name the type of reaction in which ethene is formed from chloroethane.

...............................................................................................................................(1)

(Total 7 marks)

137. This question is about the element chromium and its compounds.

(a) (i) State the full electronic configuration of a chromium atom in the ground state, using the s,p,d notation.

(1)

160

(ii) Apart from differing numbers of electrons, how does the ground state electronic configuration of chromium differ from those of the two adjacent elements in the Periodic Table, vanadium and manganese? Suggest the reason for this difference.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(b) Compounds containing the chromium(II) ion, Cr2+, are unstable in aqueous solution because they are readily oxidised by oxygen in the air.State the appropriate electrode potentials and half-cells, and use them to explain why this oxidation takes place.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(3)

(c) A useful method of stabilising an unstable oxidation state is to form a complex. You may

have prepared chromium(II) ethanoate, Cr2(CH3CO2)4(H2O)2, where the Cr2+ ion is stabilised in this way. [Details can be found on pages 464–465 of your Students’ Book.]

161

(i) Explain how water acts as a monodentate ligand in this complex.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(ii) What type of ligand is the ethanoate ion in this complex?

...............................................................................................................................(1)

(iii) Deduce the number of hydrogen peaks in the NMR spectrum of the complex from the structural formula Cr2(CH3CO2)4(H2O)2. Justify your answer.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(iv) Suggest TWO characteristic absorptions in the infra-red spectrum of the complex.

You should state the bond associated with each absorption and give the corresponding absorption value in wavenumbers.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

162

(d) (i) When first introduced, breathalysers used acidified sodium dichromate(VI) crystalsto detect ethanol on the breath. Using oxidation numbers, or otherwise, balance the equation for the reaction.

C2H6O + Na2Cr2O7 + H2SO4 → C2H4O + Cr2(SO4)3 + H2O + Na2SO4

(2)

(ii) State the colour change you would expect to see if exhaled air containing an excessive amount of ethanol reacted with the breathalyser chemicals.

................................................................................................................................(1)

(iii) What hazard is associated with the use of sodium dichromate(VI)?

................................................................................................................................

................................................................................................................................(1)

(Total 17 marks)

138. The element bromine has an atomic number of 35 and has two isotopes of relative isotopic mass79 and 81.

(a) (i) Define the term relative isotopic mass.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

163

(ii) Complete the table below.

Atom Number of protons Number of neutrons

79Br

81Br

(3)

(b) Bromine gas has the formula Br2. When a sample of bromine gas was analysed in a mass

spectrometer, three peaks were obtained of m/e values of 158, 160 and 162.

Give the formulae of the species responsible for the peaks with m/e values 158, 160 and 162.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

(Total 8 marks)

139. (a) Complete the electronic configuration of an

Al atom ls2...............................................................................................................

Al3+ ion ls2................................................................................................................(2)

(b) Describe the structure of aluminium metal and explain why it conducts electricity.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

164

(c) (i) Define the term first ionisation energy.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(ii) Explain why the first ionisation energy of aluminium is less than that of magnesium.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 10 marks)

165

140. You may find the following table useful in answering the question below.

Element Electronegativity

Hydrogen 2.1

Oxygen 3.5

Draw a diagram to show a hydrogen bond between two water molecules and explain why it forms.

Diagram

Explanation ..........................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................(Total 4 marks)

166

141. (a) Hydrogen iodide, HI, has a boiling temperature of –35 C, and hydrogen chloride, HCl, a boiling temperature of –85 C.

(i) Draw a dot and cross diagram of a hydrogen iodide molecule (showing outer shell electrons only).

(2)

(ii) Explain why hydrogen iodide has a higher boiling temperature than hydrogen chloride.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(b) Hydrogen iodide and hydrogen chloride react with water to form acidic solutions.

(i) Write the equation for the reaction of hydrogen iodide with water.

.........................................................................................................................(1)

(ii) State why the solution formed is acidic.

......................................................................................................................(1)

167

(c) (i) Excess dilute hydrochloric acid reacts with a lump of calcium oxide, CaO, to form an aqueous solution of calcium chloride.

Write the equation for this reaction, including state symbols.

......................................................................................................................(2)

(ii) In a similar reaction with dilute sulphuric acid and a lump of calcium oxide, the reaction stops after a short time even though some calcium oxide remains. State why the reaction stops so quickly.

......................................................................................................................

......................................................................................................................(1)

(Total 10 marks)

142. (a) Draw diagrams to show how the following bonds are formed from atomic orbitals.

bond

bond

(2)

168

(b) (i) State the shape of a methane, CH4, molecule, and explain why it has this shape.

Shape: ...........................................................................................................

Explanation: ..................................................................................................

......................................................................................................................(3)

(ii) State the shape of a carbon dioxide, CO2, molecule, and explain why it has this

shape.

Shape: ...........................................................................................................

Explanation: ..................................................................................................

......................................................................................................................(2)

(Total 7 marks)

143. Give TWO errors in this representation of the simple model of metallic bonding in sodium.

Error 1 .................................................................................................................................

Error 2 .................................................................................................................................(Total 2 marks)

169

144. The table below shows some data for four organic compounds.

Butane Propan-1-ol Propan-2-ol Propanone

Structuralformula

CH3CH2CH2CH3 CH3CH2CH2OH CH3CH(OH)CH3 CH3COCH3

Number ofelectrons per

molecule34 34 34 32

Boilingpoint/°C

–0.5 97.2 82.4 ?

(a) The molecules of each compound contain a similar number of electrons. What type of intermolecular forces are likely to be similar in strength?

......................................................................................................................................(1)

(b) Explain why propan-1-ol boils at a higher temperature than

(i) butane

...............................................................................................................................

...............................................................................................................................(1)

(ii) propan-2-ol.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(Total 4 marks)

170

145. (a) A sample of an element can be analysed using a mass spectrometer. State how the following are achieved in this instrument:

(i) ionisation.......................................................................................................

......................................................................................................................(2)

(ii) deflection.......................................................................................................

......................................................................................................................

(b) The following data were obtained from the mass spectrum of a sample of gallium.

Peak at m/e %

69.0 60.4

71.0 39.6

Calculate the relative atomic mass of this sample of gallium, to 3 significant figures.

(2)

171

(c) An atom contains five protons and five neutrons.

(i) Give the symbol for this atom, including the mass number.

......................................................................................................................(2)

(ii) Complete the electronic configuration of this atom.

1s2 ..................................................................................................................(1)

(iii) Give the formula of the compound formed between this element and chlorine.

......................................................................................................................(1)

(Total 9 marks)

146. Phosphorus(III) chloride, PCl3, can be formed by the reaction of phosphorus and chlorine.

2P(s) + 3Cl2(g) 2PCl3(s)

(a) (i) Calculate the maximum mass of phosphorus(III) chloride, PCl3, which could be obtained from 93.0 g of phosphorus.

(3)

172

(ii) Calculate the minimum volume of chlorine required to react completely with 93.0 g of phosphorus.

[One mole of gas occupies a volume of 24.0 dm3 under the conditions of the experiment].

(2)

(iii) Identify the oxidising agent in the above reaction and explain your answer.

......................................................................................................................

......................................................................................................................(2)

(b) (i) Draw a dot and cross diagram for a molecule of PCl3.

(2)

173

(ii) Draw the predicted shape of a PCl3 molecule and mark on the diagram a value for the bond angle.

(2)

(c) Suggest the name for the shape of the PCl4+ ion.

...............................................................................................................................(1)

(Total 12 marks)

174

147. (a) State the type of bonding in the following substances and draw diagrams to illustrate their3-dimensional structures.

Diamond

Bonding ..............................................................

Diagram

(3)

(b) Explain why sodium chloride conducts electricity when molten but not when solid.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 5 marks)

148. (a) (i) Define the term first ionisation energy.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

175

(ii) State and explain the general trend in the first ionisation energy across the period sodium to argon of the Periodic Table.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(b) (i) Write an equation to illustrate the process occurring when the second electron affinity of nitrogen is measured.

...............................................................................................................................(2)

(ii) Explain why the second electron affinity of any element is endothermic.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 10 marks)

149. An isotope of the element bohrium, Bh267107 , was recently discovered. How many neutrons are

there in a nucleus of this isotope?

...............................................................................................................................................(Total 1 mark)

176

150. Write the electron configuration of a magnesium atom, using the s, p, d notation.

................................................................................................................................................(Total 1 mark)

151. The industrial processes involved in the production of poly(chloroethene) are summarised in theflow chart:

ethane ethene 1,2-dichloroethane chloroethene poly(chloroethene)

(a) (i) Ethane is converted to ethene by dehydrogenation.

Write a balanced equation, including state symbols, for this equilibrium reaction.

(1)

(ii) Explain why conditions of high pressure are less favourable for ethene production.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(b) Draw a labelled diagram of an ethene molecule, showing the electron density distribution in the and bonds between the carbon atoms.

(2)

177

(c) Give a chemical test which would distinguish between ethane and ethene.

State the result of your test with ethene.

Test ..............................................................................................................................

Result ...........................................................................................................................(2)

(d) 1,2-dichloroethane is formed from ethene by reaction with chlorine.

State the type and mechanism of this reaction.

Type ...................................................................................................................................

Mechanism .........................................................................................................................(2)

(Total 9 marks)

152. Phosphine, PH3, is a hydride of the Group 5 element, phosphorus.

(a) (i) Draw a ‘dot-and-cross’ diagram of a phosphine molecule. You should include only outer shell electrons.

(1)

(ii) Draw the shape you would expect for the phosphine molecule, suggesting a value for the HPH bond angle.

HPH bond angle .......................................................................................................(2)

178

(iii) Explain the shape of the phosphine molecule you have given in your answer in (ii).

Justify your value for the HPH bond angle.

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................(2)

(b) (i) Write a balanced equation, including state symbols, for the atomisation of phosphine gas.

.............................................................................................................................(1)

(ii) Use your answer to (i) and the data below to calculate the standard enthalpy changeof atomisation of phosphine at 298 K. Include a sign and units in your answer.

ΔHοf[PH3(g)] = + 5.4 kJ mol

1

ΔHοat[½H2(g)] = +218.0 kJ mol

1

ΔHοat[P(s)] = +314.6 kJ mol

1

(3)

179

(iii) Calculate a value for the bond energy of the bond between phosphorus and hydrogen, using your answer to (ii).

(1)(Total 10 marks)

153. This question is about phosphine, PH3, and ammonia, NH3.

(a) Which compound has the stronger van der Waals forces?

Justify your answer.

.....................................................................................................................................

.....................................................................................................................................(1)

(b) (i) The boiling points of ammonia and phosphine are:

Ammonia 240 KPhosphine 185 K

Name the intermolecular force responsible for the higher boiling point of ammonia.

...........................................................................................................................(1)

180

(ii) Use displayed formulae to show this intermolecular bond between two ammonia molecules.

Clearly mark and label the bond angle between the molecules.

(2)(Total 4 marks)

154. (a) Complete the electronic configurations of the following noble gases.

(i) Neon: 1s2 .....................................................................................................(1)

(ii) Krypton: 1s2 .................................................................................................(1)

(b) Explain whether krypton or neon has the higher boiling temperature.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

181

(c) A mass spectrometer can be used to analyse a sample of a certain element.

Explain how each of the following is achieved in a mass spectrometer.

(i) Ionisation: .....................................................................................................

......................................................................................................................

......................................................................................................................(2)

(ii) Acceleration: .................................................................................................

......................................................................................................................(1)

(iii) Deflection: ....................................................................................................

......................................................................................................................(1)

(Total 8 marks)

155. (a) Define the term relative atomic mass.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(b) Give the symbol, including the atomic number and mass number, of the isotope whose

nucleus contains two more protons and three more neutrons than the isotope N147 .

...............................................................................................................................(2)

182

(c) The table below shows the first five successive ionisation energy values for an element.

Ionisation energy Value/kJ mol–1

1st 577

2nd 1820

3rd 2740

4th 11600

5th 14800

Use this data, and the Periodic Table, to suggest an element which could have produced these results. Explain your answer.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(Total 6 marks)

156. (a) Deduce the oxidation number of iodine in the following species.

(i) I2O7 .............................................................................................................................(1)

(ii) IO4 ..............................................................................................................................

(1)

183

(b) Iodine, I2, can be reduced to iodide ions, I–, by tin(II) ions, Sn2+, which are themselves

oxidised to tin(IV) ions, Sn4+.

(i) Construct the oxidation and reduction half-equations for the above system.

......................................................................................................................

......................................................................................................................(2)

(ii) Use the above half-equations to construct the overall ionic equation for the reaction.

......................................................................................................................

......................................................................................................................

......................................................................................................................(1)

(Total 5 marks)

157. (a) Define the term oxidising agent in terms of electron transfer, and suggest which element in Group 7 is the strongest oxidising agent.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(b) Chlorine can react with hydroxide ions to produce chloride ions, chlorate(l) ions and water.

(i) Write the ionic equation for this reaction. There is no need to include state symbols.

......................................................................................................................(2)

(ii) What type of reaction is taking place in (b)(i)?

......................................................................................................................(1)

184

(c) (i) Write an equation for the reaction between concentrated sulphuric acid and solid sodium chloride.

......................................................................................................................(1)

(ii) State ONE observation that you would make.

......................................................................................................................

......................................................................................................................(1)

(d) Draw the shapes of the following molecules, and mark on the diagram the value of the bond angles in each case.

(i) BCl3

(2)

185

(ii) PCl5

(3)(Total 12 marks)

158. Explain each of the following.

Silicon and phosphorus are both covalent substances, but silicon has a much higher melting temperature than phosphorus.

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................(Total 5 marks)

186

159. (a) State the meaning of the following terms:

(i) electrophile;

......................................................................................................................

......................................................................................................................(1)

(ii) free radical;

......................................................................................................................

......................................................................................................................(1)

(iii) nucleophile.

......................................................................................................................

......................................................................................................................(1)

(b) Classify the following reactions:

(i) chloroethane with aqueous sodium hydroxide;

......................................................................................................................

......................................................................................................................(2)

(ii) ethane with chlorine;

......................................................................................................................

......................................................................................................................(2)

(iii) ethene with hydrogen bromide.

......................................................................................................................

......................................................................................................................(2)

(Total 9 marks)

187

160. (a) Draw a ‘dot-and-cross’ diagram for a magnesium ion.

Show ALL the electrons present and give the charge on this ion.

(2)

(b) Why do salts containing magnesium ions give no colour in a flame test?

....................................................................................................................................

....................................................................................................................................(1)

(Total 3 marks)

161. The element gallium has two isotopes.

Ga6931 Ga71

31

(a) (i) State ONE similarity and ONE difference between these two isotopes in terms of the numbers of their fundamental particles.

Similarity ..........................................................................................................

Difference .........................................................................................................(2)

188

(ii) The molar mass of a sample of gallium is 69.8 g mol–1.

Calculate the percentage abundance of the isotope Ga6931 in the sample.

(2)

(b) The first four ionisation energies of gallium are plotted below.

(i) Write the chemical equation, with state symbols, which corresponds to the first ionisation energy of gallium.

(2)

189

(ii) Why is there a general rise in the ionisation energy as successive electrons are removed?

..........................................................................................................................

..........................................................................................................................(1)

(iii) Explain why there is a comparatively large increase in value between the third and fourth ionisation energies.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(c) (i) Suggest the formula of gallium chloride.(You may find it helpful to refer to the Periodic Table.)

..........................................................................................................................(1)

(ii) Gallium chloride dissolves in water to form a solution containing ions.

Suggest an experiment to show that the solution contains ions. State the result you would expect.

Experiment .......................................................................................................

..........................................................................................................................

..........................................................................................................................

Result ...............................................................................................................(2)

(Total 12 marks)

190

162. This question is about the compounds of Group 6 elements with hydrogen.

The table below shows some of the boiling points and molar masses of these hydrides.

Hydride Boiling point /K Mass of 1 mole /g

Water, H2O –– 18

Hydrogen sulphide, H2S 212 34

Hydrogen selenide, H2Se 232 ––

Hydrogen telluride, H2Te 271 130

(a) What is the mass of one mole of hydrogen selenide, H2Se?Use the Periodic Table as a source of data.

(1)

191

(b) (i) Plot a graph of the boiling points of the three hydrides H2S, H2Se, and H2Te againsttheir molar masses.

3 0 0

2 5 0

2 0 0

1 5 0

T e m p e r a t u r e/ K

2 0 4 0 6 0 8 0 1 0 0 1 2 0

M a s s o f 1 m o l e / g(2)

192

(ii) Why do the boiling points of these hydrides increase as the molar mass increases?

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(c) (i) Use your graph to predict the boiling point of water if it were to follow the pattern of the other three hydrides.

..........................................................................................................................(1)

(ii) What causes the boiling point of water to be 373 K, rather than your answer in (i)?

..........................................................................................................................

..........................................................................................................................(1)

(iii) Explain why this arises in water and not in the other hydrides.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(1)

(iv) Give the names of TWO other hydrides which, like water, have boiling points higher than you would expect.

..........................................................................................................................

..........................................................................................................................(2)

193

(d) Give TWO properties of water, other than high melting and boiling points, which are brought about by the strong intermolecular forces between water molecules.

..........................................................................................................................

..........................................................................................................................(2)

(Total 12 marks)

163. (a) State the meaning of the terms

(i) relative atomic mass

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(ii) mass number

..........................................................................................................................

..........................................................................................................................(1)

(iii) isotopes

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

194

(b) The isotopic composition of a sample of sulphur is found using a mass spectrometer.

(i) Explain how atoms of the sample of sulphur are ionised.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(ii) State the type of charge on the sulphur ions formed in the mass spectrometer.

..........................................................................................................................(1)

(iii) State how the resulting sulphur ions are then accelerated.

..........................................................................................................................(1)

(c) For a particular sample of sulphur atoms the following isotopic composition was recorded.

Isotope Percentage composition

32S 95.00

33S 0.76

34S 4.24

195

Calculate the relative atomic mass of this sample of sulphur. Give your answer to two decimal places.

(2)

(d) Predict the electronic configuration of a 34S atom, using s, p and d notation.

1s2 .........................................................................................................................(1)

(Total 12 marks)

164. (a) State and explain the trend in the boiling temperatures of the noble gases.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

196

(b) The graph below shows the melting temperatures of the elements of Period 3 of the Periodic Table, sodium to argon, plotted against atomic number.

N a M g A l S i P S C l A r

e l e m e n t

me

ltin

g t

emp

era

ture

/ K

1 8 0 0

1 6 0 0

1 4 0 0

1 2 0 0

1 0 0 0

8 0 0

6 0 0

4 0 0

2 0 0

0

(i) Identify one of the elements above that is composed of simple molecules at room temperature.

......................................................................................................................(1)

(ii) Silicon has a giant atomic structure. Explain how this structure results in the high melting temperature shown on the graph.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

197

(iii) Explain why the melting temperature of magnesium is higher than that of sodium.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(Total 9 marks)

165. (a) State the shape of a water molecule and explain why it has this shape.

Shape .....................................................................................................................

Explanation ............................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

(b) Predict the shape of the H3O+ ion and draw a diagram to illustrate its shape.

Shape ....................................................................................................................

Diagram

(2)

198

(c) (i) Use water as an example to explain what is meant by the term hydrogen bond.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(ii) State the difference in density between solid ice and liquid water and describe how the presence of hydrogen bonds accounts for this.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(Total 11 marks)

166. (a) (i) A fluoride of phosphorus, Y, contains 24.6% by mass of phosphorus and has a

molar mass of 126 g mol–1. Deduce the molecular formula of Y.(4)

(ii) Draw the shape of a molecule of compound Y. Show the values of the bond angles on the diagram.

(3)

(iii) Compound Y was converted into the ion PF6–. Draw and name the shape of PF6

– and suggest a value for the bond angles.

(3)

199

(b) (i) Consider the following data, which shows the formulae and boiling temperatures ofthe Group 7 hydrides.

Group 7 hydride Boiling temperature/°C

HF 19

HCl –85

HBr –68

HI –35

Suggest why hydrogen fluoride, HF, has the highest boiling temperature of the Group 7 hydrides.

(3)

(c) When hydrogen fluoride is dissolved in water a solution of a weak acid is formed. Write the expression for the acid dissociation constant, Ka, for hydrogen fluoride. Calculate the

value of Ka, with units, given that a 0.150 mol dm–3 solution of hydrogen fluoride has a pH of 2.04.

(5)(Total 18 marks)

167. (a) An atom of gallium has mass number 69.

Complete the table to show the number of sub-atomic particles in this gallium atom.

Electrons Neutrons Protons

(2)

200

(b) The mass spectrum of a sample of gallium is shown below.

6 9 7 1 M a s s / c h a r g e r a t i o

6 0

4 0

2 0

R e l a t i v ea b u n d a n c e

What is the average relative atomic mass of gallium in this sample? Give your answer to three significant figures.

(2)

(c) What type of bonding would you expect to find in gallium?

......................................................................................................................................(1)

(Total 5 marks)

168. (a) A few crystals of potassium bromide were dissolved in water in a test tube. A few drops of aqueous chlorine solution were then added and a colour change was observed.

(i) What colour are potassium bromide crystals?

..........................................................................................................................(1)

(ii) What colour was the solution after the chlorine solution had been added?

..........................................................................................................................(1)

201

(iii) Write a balanced ionic equation for the reaction of bromide ions with chlorine solution.Do not include spectator ions in your equation.

..........................................................................................................................(1)

(iv) What would you expect to see if the contents of the test tube were shaken with a small quantity of a hydrocarbon solvent and then allowed to settle?

..........................................................................................................................

..........................................................................................................................(2)

(b) (i) Hydrogen bromide can be made by bubbling hydrogen sulphide gas into liquid bromine.The equation for the reaction is:

2H2S(g) + 3Br2(l) 4HBr(g) + S2Br2(l)

Two elements show changes in oxidation number during this reaction.Identify these elements, stating their original and final oxidation numbers.

First element.......................................

Initial oxidation number.............. Final oxidation number .........................

Second element ..................................

Initial oxidation number.............. Final oxidation number .........................(3)

(ii) The equation shows that 2 moles of hydrogen sulphide molecules react with 3 moles of bromine molecules. Show how your answers to (i) agree with this ratio.

(1)

202

(c) The boiling points of three hydrogen halides are given in the following table:

CompoundBoiling point

/K

HF 293

HBr 206

HI 238

(i) Explain why hydrogen iodide has a higher boiling point than hydrogen bromide.

..........................................................................................................................

..........................................................................................................................(2)

(ii) Explain why hydrogen fluoride has a higher boiling point than either hydrogen bromide or hydrogen iodide.

..........................................................................................................................

..........................................................................................................................(1)

(iii) Predict the boiling point, in K, of hydrogen chloride.Justify your prediction.

Predicted boiling point.........................

Justification ......................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(Total 14 marks)

203

169. The quality of written communication will be assessed in this question. To gain full marks you must explain your ideas clearly using equations and diagrams where appropriate.

This question is about hydroxylamine, NH2OH.

Hydroxylamine can be thought of as being derived from ammonia, NH3, by the replacement of one hydrogen atom by a hydroxyl, OH, group.

(a) Draw a ‘dot-and-cross’ diagram for hydroxylamine.Use it to predict the HNH and NOH bond angles.

HNH bond angle .......................................................................................................

NOH bond angle .......................................................................................................(3)

(b) (i) What would you expect the pH of an aqueous solution of hydroxylamine to be? Justify your answer and write an equation for the equilibrium reaction between water and hydroxylamine.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(3)

(ii) Would you expect hydroxylamine to form complexes with transition metal ions?Justify your answer.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(1)

204

(c) The following experiment was carried out to determine the equation for the reaction

between iron(III) ions, Fe3+(aq), and hydroxylamine, NH2OH(aq).

250 cm3 of an aqueous solution, containing 0.370 g of hydroxylamine, was prepared

using a volumetric flask. 25.0 cm3 of this solution was reacted with excess acidified iron(III) sulphate solution.

The iron(II) ions produced were converted back to iron(III) ions by titrating with potassium manganate(VII) solution. The equation for this reaction is:

5Fe2+(aq) + MnO4 (aq) + 8H+(aq) 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

22.4 cm3 of 0.0200 mol dm–3 potassium manganate(VII) was required.

(i) How can you detect the end-point of this titration?

..........................................................................................................................

..........................................................................................................................(1)

(ii) Calculate the number of moles of iron(II) ions which reacted with the 22.4 cm3 of potassium manganate(VII) solution. This will also be the number of moles of iron(III) ions which reacted with the hydroxylamine.

(1)

(iii) How many moles of hydroxylamine were present in the 25.0 cm3 of solution used in the titration?

(1)

205

(iv) Use your answers to (ii) and (iii) to deduce the number of moles of iron(III) ions which react with one mole of hydroxylamine.

(1)

(v) What is the oxidation number of nitrogen in hydroxylamine?

..........................................................................................................................(1)

(vi) Use oxidation numbers and the number of moles reacting, to show which of the following nitrogen products, NO, N2O, N2O4, N2, and NH3, is likely to form in the reaction between hydroxylamine and iron(III) ions.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(1)

(vii) Hence, write a balanced equation for this reaction.

(1)

206

(d) Write a cell diagram for the redox reaction between manganate(VII) ions and iron(II) ions.

5Fe2+(aq) + MnO4 (aq) + 8H+(aq) 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

Calculate Eο and comment on the position of equilibrium.

……….........................................................................................................................

……….........................................................................................................................

……….........................................................................................................................

……….........................................................................................................................

……….........................................................................................................................(3)

(Total 17 marks)

170. (a) (i) Complete the electronic configuration of calcium.

1s2 ....................................................................................................................(1)

(ii) State the number of electrons in the outer shell of an atom of chlorine.

………………………………………………………………………………..(1)

(b) (i) Write the equation for the reaction of calcium with chlorine to produce calcium chloride.

………………………………………………………………………………..(1)

207

(ii) Name the type of bonding in calcium chloride.

………………………………………………………………………………..(1)

(iii) Draw a dot and cross diagram for calcium chloride showing all the outer electrons.

(3)(Total 7 marks)

171. (a) State the number of protons, neutrons and electrons in a Li

3

7

ion.

protons: ……………… neutrons: ……………… electrons: ………………(3)

(b) The mass spectrum of lithium shows two peaks. Their mass/charge ratios and percentage abundance are shown below.

Mass/charge % Abundance

6.02 7.39

7.02 92.61

Calculate the relative atomic mass of lithium, giving your answer to three significant figures.

(2)

208

(c) Describe a test that you would do to distinguish between solid lithium chloride and solid sodium chloride. Clearly state what you would do and what you would see with both substances.

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….(3)

(Total 8.marks)

172. Both magnesium metal and molten magnesium chloride conduct electricity, but solid magnesium chloride does not.

(a) Describe the structure of magnesium metal and explain why the solid conducts electricity.

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….(3)

(b) Describe, in terms of the position and motion of the particles, what happens when some solid magnesium chloride, MgCl2, is heated from room temperature to just above its melting temperature.

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….(4)

209

(c) Explain why magnesium chloride can conduct electricity when molten, but not when solid.

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….

………….…………………………………………………………………………….(2)

(Total 9 marks)

173. Nitrogen and phosphorus are in the same group of the Periodic Table. Phosphorus and hydrogenform the compound phosphine, PH3, and nitrogen and hydrogen form ammonia, NH3.

(a) (i) State the number of bond pairs and lone pairs of electrons in a molecule of phosphine.

Bond pairs of electrons: ..................... Lone pairs of electrons: ....................(2)

(ii) Use your answer to (i) to draw the shape of the molecule and indicate on your diagram the approximate HPH bond angle that you would expect.

(2)

(b) The boiling temperature of ammonia is –33 °C and that of phosphine –88°C.

(i) List all the intermolecular forces that exist between molecules of ammonia.

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..(2)

210

(ii) Explain why the boiling temperature of phosphine is lower than that for ammonia.

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..(2)

(c) Ammonia forms a dative covalent bond with H+ ions to form the ammonium ion, NH4+.

(i) Explain what is meant by the term dative covalent bond.

………….……………….……………………………………………………..

………….……………….……………………………………………………..(2)

(ii) What part of the ammonia molecule enables it to form such a bond?

………….……………….……………………………………………………..(1)

(iii) State and explain the shape of the ammonium ion, NH4+.

………….……………….……………………………………………………..(3)

(Total 14 marks)

174. (a) The first ionisation energy of potassium is +419 kJ mol–1 and that of sodium

is +496 kJ mol–1.

(i) Define the term first ionisation energy.

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..(3)

211

(ii) Explain why the first ionisation energy of potassium is only a little less than the first ionisation energy of sodium.

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..

………….……………….……………………………………………………..(3)

(b) Potassium forms a superoxide, KO2. This reacts with carbon dioxide according to the equation:

4KO2(s) + 2CO2(g) 2K2CO3(s) + 3O2(g)

Carbon dioxide gas was reacted with 4.56 g of potassium superoxide.

(i) Calculate the amount, in moles, of KO2 in 4.56 g of potassium superoxide.

(2)

(ii) Calculate the amount, in moles, of carbon dioxide that would react with 4.56 g of potassium superoxide.

(1)

212

(iii) Calculate the volume of carbon dioxide, in dm3, that would react with 4.56 g of

potassium superoxide. Assume that 1.00 mol of a gas occupies 24 dm3 under the conditions of the experiment.

(1)

(iv) What volume of oxygen gas, in dm3, measured under the same conditions of pressure and temperature, would be released?

(1)(Total 11 marks)

175. A sample of titanium (atomic number 22) is made up of five isotopes. The sample has the following percentage composition:

Mass number

46

47

48

49

50

% composition

8.0

7.3

74.0

5.5

5.2

213

(a) (i) What is the average relative atomic mass of titanium? Give your answer to three significant figures.

(2)

(ii) What instrument would have been used to find this percentage composition?

............................................................................................................................(1)

(b) (i) Give the electronic configuration of a titanium atom, using s p d notation.

............................................................................................................................(2)

(ii) Name the part of the Periodic Table where titanium appears.

............................................................................................................................(1)

(c) Titanium occurs naturally as rutile, TiO2. One possible method of obtaining pure titaniumis to heat rutile with carbon.

TiO2(s) + 2C(s) Ti(s) + 2CO(g)

(i) What type of reaction is this?

............................................................................................................................(1)

214

(ii) Calculate ΔH for this reaction given that

ΔHfο [TiO2(s)] = –940 kJ mol–1

ΔHfο [CO(g)] = –110 kJ mol–1

Include a sign and units in your answer.

(3)

(iii) Name the law you have used in your calculation.

............................................................................................................................(1)

(iv) When titanium is manufactured by this method, explain what pollution problem arises.

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(Total 13 marks)

176. This question is about nitrogen trifluoride, NF3, and nitrogen trichloride, NCl3, which are covalent compounds. Van der Waals attractions and permanent dipole–dipole attractions exist between molecules of both compounds in the liquid state.

(a) (i) Describe how van der Waals attractions are caused.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................(1)

215

(ii) In which of the two compounds would you expect there to be greater van der Waalsattractions? Justify your answer.

............................................................................................................................

............................................................................................................................(1)

(iii) In which of the two compounds would you expect there to be the greater permanentdipole–dipole attractions? Justify your answer.

............................................................................................................................

............................................................................................................................ (1)

(iv) The boiling point of nitrogen trichloride is much higher than that of nitrogen trifluoride. How might this be explained in terms of the two types of intermolecularattractions?

............................................................................................................................

............................................................................................................................(1)

(b) The standard enthalpy change for the formation of gaseous nitrogen trifluoride is

–125 kJ mol–1.

21

N2 (g) + 1 21

F2 (g) NF3 (g) Hοf = –125 kJ mol–1

The standard molar enthalpy changes of atomisation of nitrogen, N2, and of fluorine, F2, are given below.

ΔHat/kJ mol–1

21

N2 (g) N (g) + 473

21

F2 (g) F (g) + 79

216

This information can be represented on a Hess cycle in the following way, and then used to calculate bond energies.

(i) Insert formulae, showing the correct quantities of each element, into the appropriate boxes.

(1)

(ii) Insert arrows between the boxes and write the correct numerical data alongside the appropriate arrows.

(2)

(iii) Use the cycle to calculate the N F bond energy in nitrogen trifluoride.

(2)(Total 9 marks)

217

177. (a) Draw the shape of each of the following molecules and mark on the diagram a value for the bond angle in each case.

(i) CH4

(2)

(ii) NH3

(2)

(iii) BeCl2

(2)

218

(b) Name the strongest type of intermolecular force present in separate samples of each of thefollowing substances:

(i) CH4

..........................................................................................................................(1)

(ii) HF

..........................................................................................................................(1)

(c) State and explain which of the substances CH4 and HF has the higher boiling temperature.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(Total 10 marks)

178. (a) Complete the following table:

Particle Relative charge Relative mass

Proton 1

Electron –1

Neutron 1

(3)

219

(b) State the number of each of the above particles present in one molecule of CH4, showing clearly how you arrive at your answer.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

(c) Complete the electronic configuration of a chlorine atom.

1s2 ............................................................................................................................(1)

(d) Give the formula of the chlorine species composed of 17 protons, 20 neutrons and 16 electrons.

....................................................................................................................................(2)

(e) Write one equation in each case to represent the change occurring when the following quantities are measured.

(i) The first electron affinity of sulphur.

............................................................................................................................(2)

(ii) The first ionisation energy of sulphur.

........................................................................................................................(1)

220

(f) Explain why the first ionisation energy of chlorine is higher than that of sulphur.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(Total 14 marks)

179. (i) On the following diagram of a water molecule draw partial charges on each atom to showthe bond polarities:

H H

O

(1)

(ii) Explain why a water molecule has the partial charges you have drawn.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(iii) Explain whether or not a water molecule is polar overall.

....................................................................................................................................

....................................................................................................................................(1)

(Total 4 marks)

180. (a) (i) What is meant by the mass number of an atom?

..........................................................................................................................(1)

221

(ii) Define the term relative atomic mass.

..........................................................................................................................(2)

(iii) What are isotopes?

..........................................................................................................................(2)

(b) Magnesium has three isotopes. The mass spectrum of magnesium shows peaks at m/e 24 (78.60%), 25 (10.11%), and 26 (11.29%). Calculate the relative atomic mass of magnesium to 4 significant figures.

(2)(Total 7 marks)

181. (a) Define the term first ionisation energy for magnesium.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

222

(b) The logarithm of successive ionisation energies for magnesium is plotted in the graph below.

6

5

4

3

2

1

00 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

N u m b e r o f e l e c t r o n r e m o v e d

Log

ioni

sati

on e

nerg

y /k

J m

ol–1

Explain what this graph tells you about the electron arrangement in the magnesium atom.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

(c) (i) Give the full electronic configuration of magnesium using the s,p,d notation.

..........................................................................................................................(1)

(ii) Explain why all isotopes of magnesium have the same chemical properties.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(Total 9 marks)

223

182. (a) Boron forms the chloride BCl3. Draw a dot-and-cross diagram for BCl3.

(1)

(b) (i) Draw the shape of the BCl3 molecule.

(1)

(ii) Explain why BCl3 has this shape.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(c) (i) The B Cl bond is polar due to the different electronegativity of the atoms. Explain what is meant by the term electronegativity.

..........................................................................................................................

..........................................................................................................................

224

(2)

(ii) The B Cl bond is polar. Explain why BCl3 is not a polar molecule.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(Total 8 marks)

183. (a) (i) State how a flame test would distinguish between samples of calcium nitrate, Ca(NO3)2 and barium nitrate, Ba(NO3)2.

..........................................................................................................................

..........................................................................................................................(2)

(ii) Explain the origin of the flame colour.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

(3)

(b) Write the equation for the action of heat on barium nitrate.

....................................................................................................................................(2)

(c) (i) What is meant by the term polarising power as applied to cations?

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

225

(ii) Give two factors which affect the polarising power of cations.

..........................................................................................................................

..........................................................................................................................(2)

(iii) Use this information to explain why it is easier to decompose magnesium nitrate than barium nitrate by heating.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(3)

(Total 14 marks)

184. In the Periodic Table, where elements are arranged by atomic number, chlorine is a p-block element whereas manganese, a transition element, is in the d-block.

(a) (i) Define the term atomic number.

......................................................................................................................

......................................................................................................................(1)

(ii) Define the term d-block element

......................................................................................................................

......................................................................................................................(1)

226

(iii) Define the term transition element.

......................................................................................................................

......................................................................................................................

......................................................................................................................(1)

(b) The electron configuration of chlorine is 1s2 2s2 2p6 3s2 3p5. Write the electron configuration for manganese in a similar manner.

................................................................................................................................(1)

(c) (i) Define the terrm first ionisation energy of chlorine.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(ii) Sketch the pattern you would expect to see in a plot of successive ionisation energies of chlorine against the number of electrons removed.

2 4 6 8 1 0 1 2 1 4 1 6

I o n i s a t i o ne n e r g y

N u m b e r o f e l e c t r o n s r e m o v e d(3)

227

(d) Manganese(IV) oxide, MnO2, reacts with concentrated hydrochloric acid to produce chlorine, water and a salt. The salt has a composition of 43.7% manganese and 56.3% chlorine by mass.

Determine the empirical formula of the salt.

(3)(Total 12 marks)

185. Methane, CH4, chloromethane, CH3Cl, and methanol, CH3OH, have molecules with similar shapes but they have different boiling temperatures.

Compound Boiling temperature/°C

Methane –162

Chloromethane –24

Methanol +65

228

(a) Draw a dot and cross diagram to show the bonding in chloromethane. You need only draw the outer electrons of the atoms.

(2)

(b) Draw a diagram to show the shape of the chloromethane molecule and explain why it has this shape.

.................................................................................................................................

................................................................................................................................(2)

(c) Explain why the boiling temperature of chloromethane is higher than that of methane.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(4)

229

(d) Explain why the boiling temperature of methanol is higher than that of chloromethane.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(3)

(Total 11 marks)

186. (a) When the Group 2 element calcium is added to water, calcium hydroxide and hydrogen are produced.

Write an equation for the reaction.

................................................................................................................................(1)

(b) State the trend in solubility of the hydroxides of the Group 2 elements as the atomic mass of the metal increases.

................................................................................................................................(1)

(c) (i) Define the term first ionisation energy, and write an equation to represent the change occurring when the first ionisation energy of calcium is measured.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(4)

230

(ii) State and explain the trend in the first ionisation energy of the Group 2 elements.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................(3)

(Total 9 marks)

187. (a) When a sample of copper is analysed using a mass spectrometer, its atoms are ionised andthen accelerated.

(i) Explain how the atoms of the sample are ionised.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(ii) State how the resulting ions are then accelerated.

......................................................................................................................

......................................................................................................................(1)

(b) For a particular sample of copper two peaks were obtained in the mass spectrum.

Peak at m/e Relative abundance

63 69.1

65 30.9

(i) Give the formula of the species responsible for the peak at m/e = 65.

......................................................................................................................(1)

231

(ii) State why two peaks, at m/e values of 63 and 65, were obtained in the mass spectrum.

......................................................................................................................(1)

(iii) Calculate the relative atomic mass of this sample of copper, using the table of results above.

(2)(Total 7 marks)

188. Deduce and draw the shapes of the following molecules or ions. Suggest a value for the bond angle in each case. Give a brief explanation of why each has the shape you give.

(a) SF6

................................................................................................................................

................................................................................................................................(3)

(b) PH3

................................................................................................................................

................................................................................................................................(3)

232

(c) PF4

................................................................................................................................

................................................................................................................................(3)

(Total 9 marks)

189. (a) (i) Define the terms:

atomic number ...............................................................................................

......................................................................................................................

mass number .................................................................................................

......................................................................................................................(2)

(ii) Identify the particle which contains 11 protons, 12 neutrons and 10 electrons.

......................................................................................................................(1)

233

(b) Bromine consists of two isotopes, mass numbers 79 and 81. A sample of bromine gas, Br2, was examined in a mass spectrometer. The mass spectrum showing the molecular ions is given below.

1 0 0

5 0

R e l a t i v ei n t e n s i t y

1 5 8 1 6 0 1 6 2m / e

(i) Identify the species responsible for the peak at m/e = 160.

......................................................................................................................(1)

(ii) Deduce the relative abundances of the two isotopes,

(2)

(c) Define the term first electron affinity for bromine atoms, illustrating your answer with an equation.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(3)

234

(d) The graph showing the variation of the first ionisation energies of the elements neon to potassium is given below.

2 5 0 0

2 0 0 0

1 5 0 0

1 0 0 0

5 0 0

0

F i r s ti o n i s a t i o ne n e r g y / k J m o l – 1

N e N a M g A l S i P S C l A r K

(i) Define the term first ionisation energy with reference to neon.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(ii) Explain the general trend in the first ionisation energies of the elements sodium to argon.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(iii) Explain why the first ionisation energy of neon is greater than the first ionisation energy of argon.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 15 marks)

235

190. Hydrogen forms compounds with most non-metallic elements and with some metals.

(a) Calculate the empirical formula of the compound used in the manufacture of artificial rubber which has the following composition by mass.

Hydrogen 11.1% Carbon 88.9%

(3)

(b) The boiling temperatures of hydrogen chloride and hydrogen iodide are:

Hydrogen chloride –85ºC

Hydrogen iodide –35ºC

Explain why hydrogen iodide has a higher boiling temperature than hydrogen chloride.

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(c) Draw and explain the shapes of:

(i) the PH3 molecule;

......................................................................................................................

......................................................................................................................(2)

236

(ii) the AlH4– ion.

......................................................................................................................

......................................................................................................................(2)

(d) Calculate the number of molecules in 8.0 cm3 of gaseous phosphine, PH3, at room temperature and pressure.

(The molar volume of a gas at room temperature and pressure should be taken as 2.4 ×

104 cm3 mol–1. The Avogadro constant is 6.0 × 1023 mol–1.)

(2)(Total 11 marks)

191. (a) Define:

(i) the standard enthalpy of formation of benzene, C6H6(l);

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

237

(ii) the standard enthalpy of combustion of benzene, C6H6(l).

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(b) Calculate the standard enthalpy of formation of benzene, C6H6(l), using the following enthalpy of combustion data:

Substance Hc /kJ mol–1

C6H6(l) –3273

H2(g) –286

C(s) –394

(3)

238

(c) If the standard enthalpy of formation is calculated from average bond enthalpy data assuming that benzene has three C==C and three C––C bonds, its value is found to be

+215 kJ mol–1.Explain, with reference to the structure and stability of benzene, why this value differs from that calculated in (b). Use an enthalpy level diagram to illustrate your answer.

................................................................................................................................

................................................................................................................................

................................................................................................................................(4)

(d) Benzene reacts with bromine when gently warmed in the presence of a catalyst of anhydrous iron(III) bromide.

(i) The reaction is first order with respect to benzene and first order with respect to bromine. Write the rate equation for the reaction.

......................................................................................................................(1)

(ii) The mechanism of this reaction involves an attack by Br+ followed by loss of H+.

+

+

+

+

B r

H

H

B r

B r

B r+ H

S t e p 1 .

S t e p 2 .

239

Deuterium, symbol D, is an isotope of hydrogen, and the C––D bond is slightly stronger than the C––H bond. If step 2 were the rate-determining (slower) step, suggest how the rate of this reaction would alter if deuterated benzene, C6D6, were used instead of ordinary benzene, C6H6, and explain your answer.

......................................................................................................................

......................................................................................................................

......................................................................................................................(2)

(Total 14 marks)

192. (a) (i) Draw ‘dot and cross’ diagrams to show the electronic structure of the ammonia andof the boron trifluoride molecules. Hence deduce their shapes and suggest values for the HNH and FBF bond angles in these molecules.

(5)

(ii) Explain, in terms of the intermolecular forces involved, the variation of the boiling temperatures of the Group 5 hydrides listed below.

Hydride Boiling Temperature/ K

Ammonia, NH3 240

Phosphine, PH3 183

Arsine, AsH3 218

Stibine, SbH3 256

(5)

(b) When ammonia and boron trifluoride are mixed, an addition compound, H3NBF3, is formed.

(i) Suggest how the nitrogen-boron bond forms between the two molecules in the addition compound.

(1)

(ii) Suggest how the HNH and the FBF bond angles would change when the addition compound forms.

(2)

240

(c) One of the early rocket fuels was hydrazine. It burns in oxygen as follows:

H2N––NH2(g) + O2(g) N2(g) + 2H2O(g)

When 1.00 kg of hydrazine is burnt in excess oxygen 1.83 × 104 kJ of heat energy is released. Use this and the average bond enthalpies below to calculate the N––N bond enthalpy.

BondBond enthalpy

/kJ mol–1 BondBond enthalpy

/kJ mol–1

N––H +388 O==O +496

NN +944 H––O +463

(4)(Total 17 marks)

193. Consider the following shapes

A B C D

Indicate by a letter (A, B, C or D) the shape of the following ions or molecules:

(i) H2O ................................

(ii) NH3 ................................

(iii) CO2 ................................

(iv) CO–2

3 .............................(Total 4 marks)

241

194. (a) Complete the table below.

E l e m e n t C h l o r i n e B r o m i n e I o d i n e

s o l i d

g r e y

S t a t e a t r o o mt e m p e r a t u r e

C o l o u r

W h a t w o u l d b es e e n o n a d d i n gt o a n a q u e o u ss o l u t i o n o fp o t a s s i u mi o d i d e

(6)

(b) Solid iodine has a simple covalent molecular structure.

(i) Define the term covalent bond.

............................................................................................................................

............................................................................................................................(2)

(ii) Explain how the covalent structure iodine leads to it having a low melting temperature (114 °C).

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................(3)

242

(c) The diagram below shows a plot of boiling temperature against relative molecular mass for four halides, HF, HCl, HBr, and HI.

3 5 03 3 03 1 02 9 02 7 02 5 02 3 02 1 01 9 01 7 01 5 0

Boi

ling

tem

per

atur

e/K

H F H C l H B r H IR e l a t i v e m o l e c u l a r m a s s

(i) Explain the increase in the boiling temperature from hydrogen chloride, HCl, to hydrogen iodide, HI.

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(ii) Explain why the boiling temperature if hydrogen fluoride, HF, is higher than the boiling temperature of hydrogen chloride, HCl.

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(Total 15 marks)

243

195. (a) Iron has several isotopes. One of them has the electronic configuration [Ar]3d64s2 , an atomic number of 26 and a mass number of 56.

(i) Which of these pieces of information would be the most use in helping a chemist decide on the likely chemical reactions of iron?

............................................................................................................................

............................................................................................................................(1)

(ii) State how many of each of the following particles is found in an atom of 56Fe.

Protons ................ electrons ................ neutrons ................(2)

(iii) What are isotopes?

............................................................................................................................

............................................................................................................................(2)

(b) The relative atomic mass of a sample of iron may be found by using a mass spectrometer to determine the isotopic composition.

(i) The diagram below represents a low-resolution mass spectrometer in which four areas have been identified. State what happens in each of these areas.

( + )S a m p l e

B

CA

D

T o v a c u u m p u m p

244

Area A ..............................................................................................................

Area B ..............................................................................................................

Area C ..............................................................................................................

Area D ..............................................................................................................(4)

(ii) In such a determination the following isotopic composition was found.

Isotope Percentage composition

54Fe 5.8

56Fe 91.6

57Fe 2.2

58Fe 0.33

Calculate the relative atomic mass of this sample of iron, giving your answer to two decimal places.

(2)(Total 11 marks)

245

196. Consider the following data for the hydrides of the Group 4 elements.

element formula ofhydride

boiling temperature

/K

relative molecular

mass

carbon CH4 109 16

silicon SiH4 161 32

germanium GeH4 185 77

tin SnH4 221 123

lead PbH4

246

(a) Represent the trend in the boiling temperature with relative molecular mass for these hydrides.

B o i l i n gt e m p e r a t u r e/ K

3 5 0

3 0 0

2 5 0

2 0 0

1 5 0

1 0 0

5 0

00 5 0 1 0 0 1 5 0 2 0 0 2 5 0

R e l a t i v e m o l e c u l a r m a s s

(2)

(b) (i) Account for the increase in boiling temperature as the relative molecular mass increases.

............................................................................................................................

............................................................................................................................(2)

247

(ii) Use your diagram in (a) to suggest a likely value for the boiling temperature of PbH4.

............................................................................................................................(1)

(iii) PbH4 is actually thermally unstable and unlikely to have the boiling temperature you have suggested. Suggest why PbH4 is thermally unstable

............................................................................................................................

............................................................................................................................(2)

(c) Predict the shape of a molecule of SiH4 and justify your prediction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(d) (i) Define the term first ionisation energy.

............................................................................................................................

............................................................................................................................(2)

248

(ii) The successive ionisation energies of silicon are given in the table below.

number of ionisation ionisation energy/kJ mol-1

1 789

2 1580

3 3230

4 4360

5 16100

6 19800

7 23800

8 29200

9 33900

10 38800

11 45900

12 505000

13 235000

14 258000

Use these data to deduce the electronic structure of silicon.

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(Total 14 marks)

197. (a) Give the principles which enable you to predict the shape of a particular molecule, given its formula. Draw dot-and-cross diagrams for SiCl4 and XeF4, and hence draw the shapesof each of these molecules.

(6)

249

(b) When 2-bromopropanoic acid, CH3CH(Br)COOH, is reacted with sodium hydroxide in aqueous solution, 2-hydroxypropanoic acid is formed. The reaction takes place by an SnI mechanism.

(i) Write an equation for the reaction between 2-bromopropanoic acid and hydroxide ions.

(1)

(ii) Explain why 2-bromopropanoioc acid can show optical isomerism. State how this could be detected.

(2)

(iii) If a single optical isomer of 2-bromopropanoic acid is reacted with sodium hydroxide, the resulting 2-hydroxypropanoic acid mixture is not optically active. Write a reaction mechanism for the reaction, and explain why optical activity is lost.

(5)

(c) Optical activity is not confined to organic compounds; chirality is also seen in some chromium compounds. 1,2-diaminoethane, H2NCH2CH2NH2, forms an octahedral

complex with chromium (III) ion. This complex ion [Cr(H2NCH2CH2NH2)3]3+ is chiral, and the structure of one isomer is shown below.

C r ³ +

N

N

NN

NN

where 1,2-diaminoethane is shown as N N.

Sketch the structure of the other isomer and say why the complex ion is chiral.(2)

250

(d) A student was given a chromium compound Z to analyse. The following information wasobtained:

Z was orange;

a solution of Z acidified with sulphuric acid converted propan 2-ol to propanone;

a solution of Z, acidified with sulphuric acid, reacted with a solution of iron(II) ions in

a 1 : 6 molar ration Z:Fe2+ to give a green solution;

on heating an alkaline solution of Z, ammonia was evolved;

Account as fully as you can for the above observations and identify Z.(9)

(Total 25 marks)

251