2007

MINISTRY OF EDUCATION, SINGAPOREin collaboration withUNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATEGeneral Certificate of Education Advanced LevelHigher 2

CHEMISTRY 9746/01

READ THESE INSTRUCTIONS FIRST

Write in soft pencil.Do not use staples, paper clips, highlighters, glue or correction fluid.Write your name, Centre number and index number on the Answer Sheet in the spaces provided unlessthis has been done for you.

Paper 1 Multiple Choice

Additional Materials: Multiple Choice Answer SheetData Booklet

October/November 2007

1 hour

There are forty questions on this paper. Answer all questions. For each question there are four possibleanswers A, B, C and D.Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet.

Read the instructions on the Answer Sheet very carefully.

Each correct answer will score one mark. A mark will not be deducted for a wrong answer.Any rough working should be done in this booklet.

This document consists of 14 printed pages and 2 blank pages.tJl·OAPO~

'SIIIIB ,..--"

~ ~l)SingapOreExaminations and Assessment Board.~~~

UNIVERSITY of CAMBRIDGEInternational Examinations

© UCLES & MOE 2007 [Turn over

2

Section A

For each question there are four possible answers, A, B, C, and D. Choose the one you consider tobe correct.

1 Naturally occurring silicon is a mixture of three isotopes, ?8Si, 29Si and 30Si. The relative atomicmass of silicon is 28.109.

What could be the relative abundance of each of the three isotopes?

A 91.1 % 28Si, 7.9 % 29Si and 1.0 0A, 30Si

B 92.2 % 28Si, 4.70/0 29Si and 3.1 % 30Si

C 95.0 % 28Si, 3.2 % 29Si and 1.8 0A, 30Si

D 96.3 % 28Si, 0.3 % 29Si and 3.4°A, 30Si

2 When iron is reacted with aqueous iron(III) ions, iron(II) ions are formed.

Assuming the reaction goes to completion, how many moles of Fe and of Fe3+(aq) would result ina mixture containing equal numbers of moles of Fe3+(aq) and Fe2+(aq) once the reaction hadtaken place?

moles of Fe moles of Fe3+(aq)

A 1 2

B 1 3

C 1 5

D 2 3

3 An excess of cold water was added to 0.3 mol of a chloride of the third period of the PeriodicTable at room temperature.

0.6 mol of HCI was formed.

Which chloride was treated?

A MgCl2 B AICl3 C PCls D SiC4

4 Use of the Data Booklet is relevant to this question.

What do the ions 368 2- and 37CI- have in common?

A Both ions have more electrons than neutrons.

B Both ions contain the same number of nucleons in their nuclei.

C Both ions have an outer electronic configuration 2s2 2p6.

D Both ions have 20 neutrons in their nuclei.

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5 The table gives the successive ionisation energies for an element X.

1st 2nd 3rd 4th 5th 6th

ionisation energy I kJ mor1 950 1800 2700 4800 6000 12300

What could be the formula of the chloride of X?

A XCI o XC4

6 Which molecule has the largest dipole?

A B c

CI/

O=C"CI

o

7 The diagram below shows the structure of part of a crystal of ice.

.... I' #

.... H ,I' H",,:/

o

H

. I'. 0

H/ \.

Which statement is correct?

A All the bond angles surrounding each oxygen atom are 120 0•

B Four electrons from each oxygen are involved in forming hydrogen bonds.

C The hydrogen bonds, shown by the dotted lines, are stronger than the O-H covalent bonds.

o The open structure of ice causes ice to be denser than water.

© UCLES & MOE 2007 9746/01/0/N/07 [Turn over

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8 A molten chloride of a Group I metal, XCl, and a molten chloride of a Group II metal, YCl2 , areseparately electrolysed using the same current for the same time.

Which statement about this experiment is correct?

A An equal number of moles of X and Y is deposited.

B Equal masses of X and Yare deposited.

C The number of moles of Y deposited is half the number of moles of X deposited.

D YCl2 gives off twice the volume of chlorine gas as XCl, measured under the same conditionsof temperature and pressure.

9 A 25 cm3 sample of 0.20 mol dm-3 Tl + NO; required 25 cm3 of 0.10 mol dm-3 acidified KMn04 to

oxidise it to Tl 3+ in solution.

What is the oxidation state of the manganese in the reduced form?

A 2 B 3 C 4 D 7

10 Some relevant redox half-equations are given in the table.

half-equation E?/V

12(aq) + 2e-~ 2I-(aq) +0.54

2H+(aq) + 02(g) + 2e-~ H20 2(aq) +0.68

H20 2(aq) + 2H+(aq) + 2e-~ 2H2O(I) +1.77

What will be observed when a few drops of acidified aqueous hydrogen peroxide are added to anexcess of aqueous potassium iodide?

A The solution turns brown and effervescence occurs.

B The solution turns brown without effervescence.

C The solution turns purple and effervescence occurs.

D The solution turns purple without effervescence.

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11 Values for the ionic product of water, Kw, at two different temperatures are given below.

temperature/DC Kw /moI2 dm-6

25 1.00 x 10-14

30 1.44 x 10-14

What is correct for pure water at 30°C?

A [H+] > [OH-]

B [H+] =1.44 x 10-7 mol dm-3

C pH<7

o pH= 7

12 The pH change when 0.100 mol dm-3 NaOH is added dropwise to 10.0 cm3 of a 0.100 mol dm-3solution of a weak acid is shown below.

Where on the graph does pH = pKa where Ka is the acid dissociation constant of the weak acid?

14

12

10

8BpH

6 A

4

2

00 2 4 6

o

C

8 10 12 14 16 18

volume ofO.100moldm-3 NaOH added/cm3

13 The pH of human blood is constant at about 7.40.

Which ion or molecule present in the human body will remove contaminating H+(aq) ions from theblood to keep the pH constant?

A C0 2-3 B HCO; C o P03

4


6

14 The reaction of manganate(VII) ions with ethanedioate ions in acid solution may be representedby the following equation.

The graph shows concentration of manganate(VII) ions against time for this reaction.

What does the shape of the graph suggest about this reaction?

A It is exothermic.

B It is endothermic.

C It shows first order kinetics.

D It produces its own catalyst.

15 What is not a trend from left to right across the elements of the third period of the Periodic Table?

A The radii of the atoms decrease.

B The oxides of the elements change from basic to acidic.

C The melting points of the elements decrease steadily.

D The compounds of the elements change from ionic to covalent.

16 The ash from burnt seaweed contains chlorides and iodides of some Group I and Group IIelements. Some seaweed ash was treated with concentrated sulphuric acid and the resultingfumes passed first through a cold tube and then bubbled through aqueous silver nitrate.

What would be observed during the experiment?

inside the cold tube with aqueous silver nitrate

A black deposit white precipitate

B black deposit yellow precipitate

C no deposit white precipitate

D no deposit yellow precipitate

© UCLES & MOE 2007 9746/01/0/N/07

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17 What is observed when magnesium chloride is added to water?

solubility in water pH of resulting solution

A dissolves 2

B dissolves 6.5

C insoluble 7

D very slightly soluble 8


Which particle contains a single unpaired electron?

A a molecule of H2S

B one of the particles formed after the heterolytic fission of a chlorine molecule

C the ammonium ion in NH4CI

D the copper ion in CuO

19 A compound X is optically active. One mole of X liberates one mole of hydrogen when it reactswith sodium.

What could be the formula of X?

A CH3CH(OH)CHO

B CH3CH(OH)C02H

C HOCH2CH(CH3)CH2OH

D HOCH2CH2C02H

20 Bupropion is an anti-depressant used in the treatment of hyperactive children and adults.

CH3

CH3fNHCH(CH3)CO-<QCH3 CI

bupropion

Which deduction about bupropion can be made from this structure?

A It contains an amide linkage.

B It gives a phenol on heating with aqueous sodium hydroxide.

C It is optically active.

D Its aqueous solution is acidic.


8

21 Aldehydes and ketones are produced industrially by the catalytic oxidation of alkenes. Forexample, ethanal is manufactured from ethene as shown.

The process is also used industrially with but-2-ene, CH3CH=CHCH3.

Which compound is obtained from but-2-ene?

A CH3CH2CHO

B CH3COCH2CH3

C CH3CH2CH2CHO

D (CH3)2CHCHO

22 Hydrogen iodide undergoes an addition reaction with propene forming 2-iodopropane. Whenpropene is bubbled through iodine monochloride, ICI, dissolved in a suitable solvent, a similarreaction occurs.

Which product will be present in the greatest yield?

A CH3CHCH2CIICI

B CH3CHCH21II

C CH3CHCH21ICI

D CH3CHCH2CIII

23 Chlorofluorocarbons (CFCs) have been widely used in aerosol sprays, refrigerators and inmaking foamed plastics, but are now known to destroy ozone in the upper atmosphere.

What will not destroy ozone, and therefore can be used safely as a replacement for CFCs?

A CHBr3

B CCl3CBr3

C CHCIFCCIF2

D CH3CH2CH2CH3

© UCLES & MOE 2007 9746/01/0/N/07

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24 A solid compound Z dissolved readily in water to give a weakly alkaline solution. On evaporationof the water, Z was recovered unchanged.

What could Z be?

A CH NWCZ-3 3

B CCl3C02Na+

C C6HsO-Na+

D H2NCH2C02H

25 Which compound reacts with ammonia?

A bromoethane

B chlorobenzene

C ethanol

D phenol

26 All the isomeric alcohols with the molecular formula CSH120 are added separately to warmalkaline aqueous iodine.

How many of the isomers will give a yellow precipitate? (Ignore stereoisomers.)

A 0 B 1 C 2 D 3

27 Which reaction yields a carbon compound incorporating deuterium, O? [0 =2H]

NaOOA CH3CH2CN •

O2°B CH3CD(OD)C02H

acidified KMn04•

heat

NaOO

© UCLES &MOE 2007

heat

9746/01/0/N/07 [Turn over

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28 N-Methyl-D-aspartic acid is a neuroprotective agent which is used in the treatment of strokes,trauma and epilepsy. Its structure is shown.

Which statement is not correct?

A It is optically active.

B It reacts with ethanol to form an ester.

C It reacts with ethanoyl chloride to form an ester.

D It reacts with phosphorus pentachloride to form an acyl chloride.

29 Which salt will be the most acidic in aqueous solution?

B C6HsNH; CZ

C K+CZ-

D NH; CZ-

30 Which structure will be present when the amino acid aspartic acid,

is in aqueous solution at pH10?

A B C D

+ + +H3NCHC02H H3NCHC02 H3NCHC02H H2NCHCO;

I I I ICH2 CH2 CH2 CH2

I I I IC02H C02H CO; CO;

© UCLES &MOE 2007 9746/01/0/N/07

11

Section B

For each of the questions in this section, one or more of the three numbered statements 1 to 3 maybe correct.

Decide whether each of the statements is or is not correct (you may find it helpful to put a tick againstthe statements that you consider to be correct).

The responses A to D should be selected on the basis of

A B C D

1,2 and 3 1 and 2 2 and 3 1 onlyare only are only are is

correct correct correct correct

No other combination of statements is used as a correct response.

31 Which systems contain delocalized electrons?

1 cyclohexene

2 graphite

3 sodium

32 Calcium reacts with water to form calcium hydroxide and hydrogen.

The standard enthalpy change for this reaction can be measured in the laboratory.

What further information is needed in order to calculate the standard enthalpy change offormation of calcium hydroxide, tiH1?

1 tiH1 for H20(I)

2 tiH1 for H2(g)

3 first and second ionisation energies of Ca

33 A theoretical reaction involves P + Q ~ product.

The rate equation is rate =k[P][QYand the units of the rate constant, k, are molY dmz s-1•

Which sets of values of x, y and z fit the above information?

x y z

1 0 -1 +3

2 1 -1 +3

3 2 -2 +6


12

The responses A to D should be selected on the basis of

A B C D




34 Which statements about the elements calcium, strontium and barium are correct?

1 The ionic radius of the M2+ ion increases from calcium to barium.

2 The magnitude of the hydration energy of the AK-+ ion increases from calcium to barium.

3 The energy required for the process M(g) ~ AK-+(g) + 2e- increases from calcium to barium.


By using the relevant I? values, which halogens will oxidise Fe2+(aq) to Fe3+(aq)?

1 chlorine

2 bromine

3 iodine


Which of the following are chemically stable when left to stand in the atmosphere?

1 A solution of potassium hexacyanoferrate(III).

2 A solution of chromium(II) chloride.

3 A mixture of aqueous sodium hydroxide and iron(II) sulphate.

© UCLES & MOE 2007 9746/01/0/N/07

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37 Capsaicin is the substance in chilli peppers which causes the hot sensation when it is eaten.

The CH30- group is inert.

Which reactions will capsaicin undergo?

1 Addition of bromine in an organic solvent causes three atoms of bromine to be incorporatedinto the molecule.

2 On heating with NaOH(aq), two moles of NaOH are used up per mole of capsaicin.

3 On heating under reflux with acidified concentrated KMn04, (CH3)2CHCHO is a product.

38 Dinoseb is a herbicide.

N02

dinoseb

Which statements about dinoseb are correct?

1 Its aqueous solution is acidic.

2 It can exist in optically active forms.

3 It reacts with ethanol in the presence of concentrated sulphuric acid to give an ester.

39 Nail varnish consists of a mixture of pigments, gloss, plasticizer and adhesive dissolved in asuitable solvent. A common solvent is a mixture of propanone and pentyl ethanoate,CH3C02(CH2)4CH3.

Which reagents will give a yellow or orange precipitate with this solvent?

1 2,4-dinitrophenylhydrazine reagent

2 alkaline aqueous iodine

3 Fehling's reagent


14

The responses A to 0 should be selected on the basis of

A B C 0




40 The diagram shows the structure of salicylic acid.

salicylic acid

Which compounds give salicylic acid on acid hydrolysis?

1

CaCl(rCI

© UCLES &MOE 2007

2

6~COCH3

9746/01/0/N/07


CANDIDATENAME

CENTRENUMBER

f

)~J= CHEMISTRY,===~'= Paper 2 Structured

;===J===J iiiiiiiiiiiiii Candidates answer on the Question Paper.iiiiiiiiiiiiii

~ Additional Materials: Data Bookletf


INDEXNUMBER

9746/02October/November 2007

1 hour 30 minutes

Write your Centre number, index number and name on all the work you hand in.Write in dark blue or black pen on both sides of the paper.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.A Data Booklet is provided.

At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.

For Examiner's Use

1

2

3

4

5

Total

This document consists of 11 printed pages and 1 blank page.•,+"'''',-,-"~ CiVilSingapore Examinations and Assessment Board.~

..... ~'.... UNIVERSITY of CAMBRIDGE::: International Examinations

@ UCLES &MOE 2007 SP (KN) T32179/5 [Turn over

1

2

When this paper is given in it will go by air to England. Intercontinental jet airliners usekerosene as fuel. The formula of kerosene may be taken as C14Hso.

(a) To which homologous series does kerosene belong?

...................................................................................................................................... [1]

(b) When kerosene burns in an excess of air, carbon dioxide and water form.Balance the following equation for the complete combustion of kerosene.

ForExaminer's

Use

............ C14Hso + 02 ~ CO2 + H20 [1 ]

(c) The flight path from Singapore to London is approximately 10700km. A typicalintercontinental jet airliner burns 10.8 kg of kerosene for each kilometre covered.

(i) Calculate the mass, in tonnes, of C14Hso burnt on a flight from Singapore to London.[1 tonne =1 000 kg]

(ii) Use your equation in (b) to calculate the mass of CO2 produced during this flight.

[3]

© UCLES & MOE 2007 9746/02l0/N/07

3

At sea level, an inflated bicycle tyre contains 670 cm3 of air at an internal pressure of6 bar and a temperature of 20°C. The instructions on the side of the tyre state 'Safety note:maximum internal pressure 8 bar.' At sea level, atmospheric pressure is 101 kPa. The tyrewill burst if the difference between the internal pressure and the external pressure becomestoo great.[1 bar = 100kPa]

(d) Use the general gas equation PV = nRT to calculate the amount in moles of air in thetyre at sea level.

[2]

Bicycles may be carried in the luggage hold of an airliner, a part of the aircraft which is notalways heated or maintained at a pressure of 101 kPa. Typical values for the conditions in theluggage hold of an airliner at a height of 10000 m are a temperature of 5 °C and a pressureof 0.28 bar.

(e) A bicycle, with the same tyre inflated at sea level as described above, is placed in thehold of the airliner.Assuming the volume of the tyre does not change, calculate the pressure inside the tyreat a height of 10000 m. Include units in your answer.

[2]

(f) Some airlines insist that bicycle tyres should be deflated before the flight, other airlinesdo not.Should the tyre described above be deflated before flight? Use the data given at the topof this page and your answer to (e) to justify your reasoning.

...................................................................................................................................... [2]

[Total: 11]

ForExaminer's

Use


2

4

Many compounds of chlorine are manufactured from brine, NaCl(aq). The electrolysis of brineproduces C12(g) and NaOH(aq). In some industrial electrolytic cells, these two substancesare allowed to react further. The products formed in this second reaction depend on theoperating conditions used.

(a) Write balanced equations for the reaction between C~(g) and

(i) cold aqueous NaOH,

(ii) hot aqueous NaOH.

[3]

(b) In each of these reactions, two different chlorine-containing compounds are formed in aredox reaction.

(i) What is the oxidation number of chlorine in each of the chlorine-containing speciesin your equation in (a)(i)? Give your answer in the spaces below.

speciesoxidation

speciesoxidation

number number

reactant 1><><products

(ii) What is unusual about this reaction?

(4]

ForExaminer's

Use

© UCLES &MOE 2007 9746/02/0/N/07

5

(c) Chlorine dioxide, Ci02, is used for bleaching paper pulp and for some water treatment.It is manufactured from CiO; ions in acid solution.

CiO; + 2H+ + e-~ Ci02 + H20

(i) This reaction may be carried out by using aqueous hydrogen peroxide, H20 2• Usethe Data Booklet to identify the half-equation for H20 2 in this reaction and write iton the line below.

(ii) Use your answer to (i) to construct the overall equation for the reaction of CiO;ions with H20 2 in acid solution.

(iii) What is the role of the H20 2 in this reaction?

[3]

[Total: 10]

ForExaminer's

Use


6

3 Cobalt forms many complexes with ligands such as H20, NHs and CI-.

The most common oxidation states of cobalt are +2 and +3.

Cations containing cobalt in these two oxidation states have significantly different colourseven when the ligands are the same.

Solutions of C0 2+(aq) contain the ion [Co(H20)6]2+.

E6 data for some cobalt complex ions are given below.

[Co(H20)6]S+ + e-~ [Co(H20)6]2+ E6 = + 1.82V

[Co(NHs)6]S+ + e-~ [Co(NH3)6]2+ E6 = + 0.11 V

[Co(H20)6]2+ + 2e-~ Co + 6H20 E6 = - O.28V

[Co(NH3)6]2+ + 2e-~ Co + 6NH3 E6 = - 0.43V

CI02 acts as a powerful oxidising agent in acid solution.

CI02 + 4H+ + 5e-~ CI- + 2H20 E6 = + 1.50V

(a) When CI02 in acid solution is mixed with Co2+(aq) no significant colour change isobserved.When Co2+(aq) is mixed with an excess of NH3(aq) a slight colour change occurs andcation P is formed.When cation P is mixed with CI02 in acid solution, a significant colour change occurs.

Use this information and the information given about cobalt above to answer the followingquestions.

(i) What is the co-ordination number of Co in [Co(H20)6]2+?

(ii) Why is no significant colour change observed when CI02 in acid solution is mixedwith Co2+(aq)? Explain your answer.

ForExaminer's

Use

© UCLES & MOE 2007 9746/02/0/N/07

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(iii) Suggest the identity of cation P.

(iv) Suggest what is formed when cation P is mixed with CI02 in acid solution andexplain why this reaction takes place.

[6]

[Total: 6]

ForExaminer's

Use


4

8

Trichloromethane, CHC~, formerly known as chloroform, was used as an anaesthetic insurgery. One reason for it not being used today is that it naturally oxidises to phosgene,COC~, which is highly toxic. .

ForExaminer's

Use

2CHC~(I) + 02(g) --7 2COC~(g) + 2HCl(g) ~H6 =-356 kJ mol-1

(a) Use the value of iiH6 given above and the data below to calculate the standard enthalpychange of formation of phosgene.

compound iiHf IkJmol-1

CHC~ (I) -134

HCl (g) -92

[2]

(b) In order to prevent the oxidation of chloroform, it is kept in dark bottles. What does thissuggest about the nature of this oxidation?

...................................................................................................................................... [1]

(c) In phosgene, the carbon atom is in the centre of the molecule and is attached to bothchlorine atoms and to the oxygen atom.

(i) Draw a 'dot-and-cross' diagram of the phosgene molecule.

(ii) Suggest the size of the Cl-C-Cl bond angle in the COCl2 molecule.

[3]

(d) Phosgene reacts with NaOH(aq).lt is suggested that the reaction occurs in two stages.

COC~ OH- t COCl(OH) Ii CO2 + HClstage stage

© UCLES &MOE 2007 9746/02l0/N/07

9

(i) What type of reaction is occurring in each stage?

stage I .

stage II .

(ii) Suggest a mechanism for stage I. In your answer, show any relevant charges, lonepairs of electrons and movement of electrons.

[5]

(e) In order to remove any phosgene present in a bottle of chloroform, a small amount ofethanol is added. Use the information in (d) to suggest the structural formula of theorganic compound formed when phosgene reacts with ethanol.

[1 ]

(f) Phosgene can be converted into urea, CO(NH2)2.

(i) Suggest a reagent for this conversion.

(ii) With strong acids urea can act as a base. Suggest why.

[2]

(g) Granular urea can be used to remove N02 from the flue gases of power stations wherehydrocarbon fuels are burned in air. Carbon dioxide, water and nitrogen are formed.

(i) Write a balanced equation for this reaction.

(ii) Why is it important to remove N02 from the flue gases?

[2]

[Total: 16]

ForExaminer's

Use

© UCLES & MOE 2007 9746/02JO/N/07 [Turn over

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10

The spice cinnamon has been used as a medicine for many hundreds of years.However, recent research has suggested that cinnamon could also be an effective pesticideagainst the larvae of mosquitoes, thus helping in the fight against malaria.

ForExaminer's

Use

Each of the following four compounds, which are present in cinnamon, appears to be effectiveas a pesticide.

CH=CHCHO 6CHCH,oCOCH. OH CH=CHCHa

6 OCHa

CH2CH=CH2 OCHa

A B C D

The group -OCHa which is present in compounds C and D can be regarded as inert.

(a) Only one of the compounds A, B, C or D will react with each of the following reagents.In each case identify the compound concerned and draw the structural formula of theorganic product formed.Each compound may be used once, more than once, or not at all.

reagentcompound structural formula

A, B, Cor D of the organic product

CHaCOCl

dilute HN03

Na

Tollens' reagent

[8]

© UCLES & MOE 2007 9746/02l0/N/07

11

(b) Draw the structural formulae of the organic compounds formed when

(i) compound C is mixed with aqueous bromine;

(ii) compound D is heated under reflux with hot concentrated manganate(VII) ions.

[4]

(c) Compound A may be converted into compound B in a two-stage process.

(i) What is the structural formula of the intermediate in this conversion?

(ii) For each stage, in the reaction sequence, give reagent(s) and conditions.

stage I

reagent(s) .

conditions .

stage II

reagent(s) .

conditions .[5]

[Total: 17]

ForExaminer's

Use

© UCLES & MOE 2007 9746/02JO/N/07

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BLANK PAGE

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Everyreasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, thepublisher will be pleased to make amends at the earliest possible opportunity.

University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University ofCambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

9746/02JO/N/07


CHEMISTRY 9746/03Paper 3 Free Response

Candidates answer on separate paper.

Additional Materials: Answer PaperData Booklet


Write your Centre number, index number and name on all the work you hand in.Write in dark blue or black pen on both sides of the paper.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

October/November 2007

2 hours

Answer any four questions.A Data Booklet is provided.You are reminded of the need for good English and clear presentation in your answers.

The number of marks is given in brackets [ ] at the end of each question or part question.At the end of the examination, fasten all your work securely together.

This document consists of 11 printed pages and 1 blank page.~+o,.,

-~~ 'iiii\Singapore Examinations and Assessment Board.~

UNIVERSITY ofCAMBRIDGEInternational Examinations

© UCLES & MOE 2007 SP (KN) T32390/3 [Turn over

2

Answer any four questions.

1 The "OXO" reaction (reaction I in the scheme below) is industrially important for making alcohols,aldehydes and carboxylic acids. For example, butan-1-ol, butanal and butanoic acid can all besynthesised from propene, C3Hs' according to the following scheme.

propene

CH3CH2CH2C02H

Y butanoic acidCHaCH2CH2CHO(g)

butanal ~CH3CH2CH2CH20H

butan-1-01

(a) Write an expression for Kp for reaction I, stating its units. [2]

(b) When an equimolar mixture of CaHs' CO and H2 at an initial total pressure of 120atm isallowed to reach equilibrium at SOOK, the partial pressure of butanal is found to be 39.6atm.

(i) Calculate the equilibrium partial pressures of C3Hs' CO and H2•

(ii) Hence calculate a value for Kp at 500 K.

(iii) Suggest, with a reason, whether or not a higher pressure would favour the formation ofbutanal.

(iv) Predict the sign of liS for reaction I, showing your reasoning.

(v) The value of ~G for this reaction is negative. Use this information, together with youranswer to part (iv), to predict the sign of IiH for reaction I. Explain your reasoning.

(vi) An approximate value for IiH can be calculated using bond energy values. Taking thebond energy for the C=O bond in carbon monoxide to be 1077kJ mol-1, and usingother appropriate bond energies given in the Data Booklet, calculate the value of IiH forreaction I.

[7]

© UCLES & MOE 2007 9746/03/0/N/07

3

(c) (i) State the reagents and conditions needed for

• reaction II,

• reaction III.

(ii) State the reagents and conditions needed for the conversion of butan-1-01 into

• 1-bromobutane,

• 2-bromobutane (in two steps).[5]

(d) The compound 2-bromobutane is a useful intermediate for making other organic compounds.

(i) It forms butan-2-ol by heating with NaOH(aq).How would you expect the rate of this reaction to compare to that of the reaction of2-iodobutane with NaOH(aq)? Explain your answer.

(ii) Suggest the intermediates and products formed during the following reactions of2-bromobutane.

•

•

reaction with NaCN in alcohol, followed by LiAlH4

reaction with NaOH in ethanol, followed by cold KMn04(aq)[4]

(e) When butane is treated with a small quantity of bromine in the presence of ultraviolet light, both1-bromobutane and 2-bromobutane are produced. Suggest, with a reason, the approximateratio in which they are formed. [2]

[Total: 20]


4

2 (a) Sketch a graph showing the variation of first ionisation energy across the third period of thePeriodic Table, and explain qualitatively its shape. [3]

The oxides MgO, A~03 and Si02are all used as refractory materials due to their high melting points.The last two are major constituents of gemstones, such as rubies, sapphires and amethysts.

(b) If a sample of one of the oxides was provided as a white powder, describe the reactions youcould carry out on the powder to determine which of the three oxides it was. [3]

(c) When sodium chloride is added to water, a solution is formed which has a pH of 7. Whenphosphorus pentachloride is added to water, the resulting solution has a pH of 1. Explainthese observations, and why these two chlorides differ in their reaction with water. [2]

(d) Sulphur dichloride oxide (thionyl chloride), SOC~, is a useful reagent in organic chemistry,converting -OH groups into -Cl groups.

R-OH + SOC~ --.. R-Cl + HCl + S02

(i) Suggest and explain one precaution you should employ when using SOC~ in thelaboratory.

(ii) Suggest the equation for the reaction of SOC~with water.

(iii) Suggest what you would see when the following are added to separate portions of thesolution resulting from the reaction of SOC~ with water.

• a few drops of AgN03(aq)

• a few drops of K2Cr20 7(aq)

Write equations for any reactions that occur.[6]

© UCLES & MOE 2007 9746/03/0/N/07

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(e) (i) Suggest structures for compounds A and B in the following scheme.

SOC~ NH3 O=jNHA .. B .. + 2HCl

C8H604 C8H402C~ 0

C

Compound C is a useful intermediate for making primary amines from bromoalkanes, by thefollowing method.

O=jNHo

c

II

III

o

(ii) What types of reaction are reactions I, II and III?

(iii) Suggest reagents and conditions for reaction III.

o

OH

OH

[6]

[Total: 20]

© UCLES &MOE 2007 9746/03/0/N/07 [Turn over

6

3 (a) Calcium fluoride, CaF2, occurs naturally in the mineral fluorspar. It is the major source offluorine for the chemical industry, for making PTFE, freons and fire retardants.

(i) Use the following data, together with relevant data from the Data Booklet, to calculate avalue for the lattice energy of CaF2(s).

enthalpy change of atomisation of Ca(s) +178 kJ mol-1

electron affinity of fluorine atoms -328 kJ mol-1

enthalpy change of formation of CaF2(s) -1220 kJ mol-1

(ii) Suggest, with reasons, how the magnitude of the lattice energy of CaF2(s) might compareto that of

• CaC~(s)

• CaO(s).[5]

(b) Calcium fluoride is sparingly soluble in water. In its saturated solution, the concentration ofCaF2 is 2.3 x 10-4 moldm-3•

(i) Write an expression for the solubility product, Ksp' of calcium fluoride, and calculate itsvalue.

(ii) Use the following data, together with relevant data given in part (a)(i), to calculate a valuefor the enthalpy change of solution of calcium fluoride.

ion ~He /kJ mol-1f

Ca2+(aq) -543

F-(aq) -333

(iii) Use your answer to part (ii) to predict whether CaF2 will be more, or less, soluble in hotwater than in cold.

[5]

(c) The melting point of beryllium nitrate, Be(N03)2' is 60 ac, whereas that of calcium nitrate is561 ac. Magnesium nitrate does not have a recorded melting point because on heating itdecomposes before it melts.

(i) Use these data to suggest the nature of the bonding in beryllium nitrate and in calciumnitrate, explaining your answer.

(ii) Write an equation for the thermal decomposition of magnesium nitrate, and explain whycalcium nitrate has to be heated to a higher temperature before it decomposes.

[5]

© UCLES & MOE 2007 9746/03/0/N/07

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(d) In 1834 the French chemist Eugene Paligot published his investigations into the action of heaton the Group II salts of carboxylic acids. He discovered that the salts decomposed to give themetal carbonate and a carbonyl compound. Thus calcium ethanoate produces propanone.

heat

When this reaction is carried out by heating a 1:1 molar mixture of calcium ethanoate andcalcium methanoate, (HC02)2Ca, a mixture of three carbonyl compounds is formed, all havingMr < 60.

(i) Suggest the structures of the three carbonyl compounds, and the ratio in which theymight be produced.

(ii) Suggest two chemical tests that could be used to distinguish the three carbonylcompounds from each other. You should state what you would observe for eachcompound in each test.

[5]

[Total: 20]

© UCLES &MOE 2007 9746/03/0/N/07 [Turn over

8

4 (a) (i) Write an expression for the acid dissociation constant, Ka, for the weak acid hydrocyanicacid, HCN.

(ii) For HCN, Ka = 4.9 x 10-10 mol dm-3. Use this value to calculate [H+] ina 0.100 mol dm-3 solution of HCN, and hence calculate the percentage of HCN moleculesthat are ionised.

(iii) Explain how the addition of solid sodium cyanide, NaCN, will alter the percentage ofHCN molecules ionised.

[5]

(b) (i) What is understood by the term order of reaction?

Cyanohydrins are useful intermediates in organic syntheses. They can be made by reactingketones with a solution of HCN to which a small amount of NaCN has been added.

NaCN(CH3)2CO + HCN -~JI (CH3)2C(OH)CN

In a series of experiments, the reaction was carried out with different concentrations of thethree reagents, and the following relative initial rates were obtained.

experiment [(CH3)2CO] [HCN] [NaCN] relative initial ratenumber Imoldm-3 Imoldm-3 Imoldm-3 Imoldm-3 S-1

1 0.040 0.040 0.008 1.00

2 0.050 0.040 0.008 1.25

3 0.040 0.040 0.006 0.75

4 0.050 0.050 0.006 0.94

(ii) Use these data to deduce the order of reaction with respect to each of the three reagents,showing how you arrive at your answers. Hence write a rate equation for the reaction.

(iii) Describe a mechanism that is consistent with your rate equation, and indicate which stepin the mechanism is the rate determining step. Explain your reasoning.

(iv) Hence suggest why propanal, CH3CH2CHO, reacts with HCN at a faster rate than doespropanone.

(v) State the roles of HCN and NaCN in the mechanism of this reaction.[10]

© UCLES &MOE 2007 9746/03/0/N/07

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(c) The reaction between propanal and HeN produces an equimolar mixture of two isomersD and E. When the v~pour of either isomer is passed over hot aluminium oxide, the samemixture of two cyanoalkene isomers F and G is produced.

• Describe the types of isomerism shown here.

• Explain why each of the two isomers D and E produce the same mixture ofcyanoalkenes.

You should include the displayed formulae of all the compounds D - G in your answer. [5]

[Total: 20]


10

5 (a) (i) Describe the requirements needed for two molecules to form a hydrogen bond betweenthem, illustrating your answer with a suitable example.

(ii) The first four members of the series of carboxylic acids represented by the generalformula H-(CH2)n-C02H (n =0, 1, 2, 3...) are fully soluble in water, but as the value of nincreases from 4 upwards, the acids become increasingly insoluble.

By considering the relevant interactions between the molecules of the carboxylic acidswith each other, and also with the solvent, suggest reasons for this decreasing solubility.

[6]

(b) Human serum albumin, HSA, is an important protein that transports long chain fatty acidsand other hydrophobic molecules in the bloodstream. The HSA molecule is a single chain of570 amino acids, 67% of which are incorporated into an a-helix. It is a globular protein andtakes up a roughly spherical shape in water.

Eight of the most common amino acids in the HSA molecule are listed below.

formula of side chainnumber of amino

amino acid(R in RCH(NH2)C02H)

acids residues permolecule of HSA

glutamic acid -CH2CH2C02H 80

leucine -CH2CH(CH3)2 58

lysine -CH2CH2CH2CH2NH2 58

valine -CH(CH3)2 45

cysteine -CH2SH 36

phenylalanine -CH2CsHs 33

threonine -CH(OH)CH3 27

serine -CH2OH 22

(i) What is understood by the term primary structure of a protein?

(ii) Use three of the above amino acids to construct the displayed formula of a possiblesection of the protein chain of HSA.

(iii) Describe how a polypeptide chain is held in the shape of an a-helix.

(iv) The cysteine residues in the HSA molecule can form disulphide bridges.Illustrate this process by means of a chemical equation.Assuming all the disulphide bridges are intramolecular, how many bridges could be madewithin each HSA molecule?

© UCLES & MOE 2007 9746/03/0/N/07

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(v) The roughly spherical shape of the HSA molecule is due to the attractions between thevarious side chains. Apart from the disulphide interaction mentioned in part (iv), describetwo other types of side-chain interaction, illustrating your answer with suitable pairs ofamino acids from the table above.

(vi) Long chain fatty acids such as stearic acid (n = 17 in the general formula in part (a)(ii»)are carried through the bloodstream in the inside of the HSA molecule. Suggest twoamino acids in the above table which would interact with the long chain on stearic acid.

(vii) The amino acids whose side chains are on the outside of the HSA molecule are likelyto interact strongly with water molecules. Suggest three amino acids in the above tablewhich are likely to do this.

[14]

[Total: 20]

© UCLES & MOE 2007 9746/03/0/N/07

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9746/03/0/N/07

2007

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