institut de formation apostolique de kimihurura (ifak...

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INSTITUT DE FORMATION APOSTOLIQUE DE KIMIHURURA (IFAK) Date: 29/04/2020

CHEMISTRY HOME EXERCISES

[FOR SENIOR 3/Phase 2] Instructions:

This paper consists of two parts. Part A: Multiple choice questions, 55 questions, 1 mark for each (55 marks) Part B: Open questions, 7 questions, (65 marks)

Attempt all questions & Max.: 120 marks Use Periodic Tables

Teacher: Clément NGIRABATWARE

PART A [55 marks]

Note: To answer question 1 – 4, use the graph below Look at the solubility graph below and answer the questions that follow:

(1) How much sodium nitrate will dissolve at 60°C?

(a) 100 grams

(b) 110 grams

(c) 120 grams

(d) 130 grams (2) Which solute is the most soluble at 80°C?

(a) Sodium Chloride (b) Sodium Sulphate

(c) Sodium Nitrate (d) Potassium Nitrate

(3) Which solute is the least soluble at 10°C?

(a) Potassium Nitrate (b) Sodium Chloride

(c) Sodium Sulphate (d) Sodium Nitrate

(4) 140 grams of solute is dissolved at 80°C is true for: (a) Sodium Nitrate (b) Potassium Nitrate

(c) Sodium Sulphate (d) Sodium Chloride

(5) Which compound has the empirical formula with the greatest relative formula mass?

(a) C2H6 (b) C4H10

(c) C5H10 (d) C6H6

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(6) Choose the correct statement

(a) With increase in temperature, the saturated solution becomes unsaturated. (b) The quantity of solute dissolved in a certain quantity of solvent denotes the concentration of

solution. (c) Both (a) and (b) (d) None of these

(7) When a single product is produced from two or more reactants, the reaction is: (a) Metathesis reaction (b) Decomposition reaction

(c) Combination reaction (d) Displacement reaction

(8) When hydrocarbon compounds undergo combustion in excess of oxygen, the products are (a) Carbon dioxide and carbon monoxide (b) Carbon monoxide and water

(c) Carbon dioxide and water (d) Either (b) or (c)

(9) Which statement is true for the following reaction?

A + BC → B + AC (a) A is less reactive than B (b) A is more reactive than C

(c) A is more reactive than B (d) B is more reactive than A

(10) Salts obtained by reaction of sulphuric acid are (a) Chlorides (b) Carbonates

(c) Acetates (d) None of these.

(11) The mathematical relationship between pressure and temperature was given by

(a) Robert Boyle (b) Gay-Lussac

(c) Amedeo Avogadro (d) A.C. Charles

(12) Aluminium oxide and zinc oxide are examples of

(a) Amphoteric oxides (b) Neutral oxides

(c) Basic oxides (d) None of these

(13) Sucrose and urea are good examples of

(a) Strong electrolyte (b) Weak electrolyte

(c) Non-electrolyte (d) All of these

(14) Choose the correct statement(s). (a) Hydrochloric acid is widely used in chemical industry (b) Magnesium hydroxide is also known as milk of magnesia (c) Nitric acid is used in the manufacture of fertiliser (d) All of the above

(15) Electrolyte used in car batteries to get the electricity is (a) Sulphuric acid (b) Nitric acid

(c) Sodium acetate (d) Calcium chloride

(16) Organic chemistry deals with the compounds containing (a) Carbon (b) Phosphorus

(c) Silicon (d) Chlorine

(17) The compounds in a homologous series have

(a) Same general formula (b) Similar chemical properties

(c) Differ by a CH2 group. (d) All of these

(18) Complete combustion of a hydrocarbon produces only carbon dioxide, CO2, and water, H2O. C5H12(l) + 8O2(g) → 5CO2(g) + 6H2O(g)

When 0.1 mol of the hydrocarbon C5H12 is completely combusted, which volume of carbon

dioxide, measured at room temperature and pressure, is produced? (a) 1.2 dm3 (b) 2.4 dm3

(c) 4.8 dm3 (d) 12 dm3

(19) Which statements about endothermic reactions are correct? 1. Energy is absorbed from the surroundings. 2. Energy is released to the surroundings. 3. The temperature of the reaction mixture falls. 4. The temperature of the reaction mixture rises.

(a) 1 and 3 (b) 1 and 4

(c) 2 and 3 (d) 2 and 4

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(20) Which property shows an increasing trend in the elements, from Group I to Group VII,

across a period of the Periodic Table? (a) Ability to form anions (b) Metallic character (c) Number of electron shells (d) Reactivity with water

(21) The equation represents the reaction between two gases, X2 and Y2, to form compound XY.

X2(g) + Y2(g) →2XY(g) The energy profile diagram for the reaction is shown.

Which statement about this reaction is correct? (a) The activation energy for the reaction is equal to E. (b) The enthalpy change for the reaction is equal to E. (c) The reaction is exothermic. (d) The reaction is endothermic.

(22) Three separate mixtures of a solution and a solid are made, as shown in the table. The

mixtures are warmed. In which mixtures does gas form?

NaOH(aq) and NH4Cl(s)

H2SO4(aq) and NH4Cl(s)

H2SO4(aq) and Mg(s)

Key = gas forms = no gas forms

(a)

(b)

(c)

(d)

(23) Insoluble salts are prepared by reacting aqueous solutions of soluble salts. A precipitate forms.

Which pairs of aqueous solutions form a precipitate? 1. Barium chloride and nitric acid 2. Barium chloride and sulphuric acid 3. Barium nitrate and nitric acid 4. Barium nitrate and sulphuric acid

(a) 1 and 2 (b) 1 and 3 (c) 2 and 4 (d) 3 and 4

(24) Aluminium is used to make saucepans because of its apparent lack of reactivity. Which

property of aluminium explains its unreactivity? (a) It has a layer of oxide on its surface. (b) It has a low density. (c) It is a good conductor of electricity. (d) It is in Group III of the Periodic Table.

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(25) The diagram shows the structure of an alloy.

Which statement about alloys is correct?

(a) Alloys can only be formed by mixing copper or iron with other metals. (b) High carbon steel alloys are soft and easily shaped. (c) In an alloy there is attraction between positive ions and a ‘sea of electrons’. (d) The alloy brass has a chemical formula.

(26) Lakes contain a variety of dissolved substances. Which substance is responsible for

eutrophication in lakes? (a) Metal compounds (b) Nitrate fertilisers (c) Oxygen (d) Sulphuric acid

(27) How many of the molecules shown belong to the homologous series of alkanes? C2H4 C3H8 C4H10 C5H10 C6H14

(a) 1 (b) 2 (c) 3 (d) 4

(28) One atom of element X and two atoms of element Y react to form an ionic compound.

Element X forms a positive ion. Which elements could X and Y be?

X Y

(a) Calcium Chlorine

(b) Calcium Oxygen

(c) Sodium Chlorine

(d) Sodium Oxygen

(29) An element with a high melting point forms an oxide that is gaseous at room temperature. Which type of structure or bonding is present in the element?

(a) Giant covalent (b) Ionic (c) Metallic (d) Simple molecular

(30) Which of the following is NOT a characteristic of metals?

(a) Lustre (b) Conducts electricity (c) Brittle (d) Malleable

(31) A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. The relative molecular mass of the compound is around 60. What is the molecular formula of the compound?

(a) CH2O (b) C2H4O

(c) C2H4O2 (d) C2H6O2

(32) Which fertiliser contains the highest percentage of nitrogen by mass?

(a) Ammonium nitrate, NH4NO3; formula mass is 80 (b) Ammonium phosphate, (NH4)3PO4; formula mass is 149 (c) Ammonium sulphate, (NH4)2SO4; formula mass is 132 (d) Potassium nitrate, KNO3; formula mass is 101

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(33) The diagram shows part of the Periodic Table.

Which two letters represent elements that can react together to form covalent

compounds? (a) W and X (b) W and Y

(c) X and Y (d) Y and Z

(34) Several different treatments are used to purify the water supply. Which impurities can be removed by which treatment?

Filtration Use of carbon Chlorination

(a) Harmful microbes Solids Unpleasant odours and tastes

(b) Harmful microbes Unpleasant odours and tastes Solids

(c) Solids Harmful microbes Unpleasant odours and tastes

(d) Solids Unpleasant odours and tastes Harmful microbes

(35) Which species contains the smallest number of electrons? (a) B3+ (b) Be2+

(c) H– (d) He+

(36) Which of the following is correct? (a) Diamond is the hardest substance known. (b) Graphite has very low melting point. (c) Graphite does not conduct electricity. (d) Diamond burns on strong heating to form helium gas.

(37) When a piece of sodium is heated in air, it reacts with oxygen to form the ionic compound sodium oxide, Na2O. In terms of electrons, which statement correctly explains what

happens when sodium reacts with oxygen? (a) An oxygen atom shares two electrons with two sodium atoms. (b) A sodium atom loses two electrons which are transferred to an oxygen atom. (c) A sodium atom shares its outer shell electron with two oxygen atoms. (d) Two sodium atoms each lose one electron which are both transferred to one oxygen atom.

(38) The total number of electrons in one atom of element Q is 17 and in one atom of element R is 19. Which statement about elements Q and R is correct?

(a) Q and R react together to form a covalent compound. (b) Q forms positive ions. (c) R has more outer shell electrons than Q. (d) R is more metallic than Q.

(39) What is the correct dot-and-cross diagram for NCl3?

(a) (b) (c) (d)

(40) Magnesium oxide has a high melting point. It is used to line the inside of furnaces that operate at high temperatures. Why does magnesium oxide have a high melting point?

(a) It has metallic bonds. (b) It has strong forces between its molecules. (c) It is a simple molecular substance. (d) It is an ionic compound.

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(41) Which of the following would not react together to form a precipitate?

(a) Aqueous sodium hydroxide and aqueous ammonium chloride (b) Aqueous silver nitrate and aqueous sodium chloride (c) Aqueous sodium hydroxide and aqueous iron (II) sulphate (d) Aqueous barium nitrate and aqueous magnesium sulphate

(42) The results of two tests on solution X are shown.

Reagent added Observation on adding a few drops of reagent

Observation on adding an excess of reagent

Aqueous sodium hydroxide Aqueous ammonia

White precipitate White precipitate

Precipitate dissolves Precipitate remains

Which ion is present in solution X? (a) Al3+ (b) Ca2+

(c) Cu2+ (d) Zn2+

(43) Which diagram shows the arrangement of particles inside a balloon containing a

mixture of the gases nitrogen and oxygen?

(a) (b) (c) (d)

Key

(44) When two elements react together, a compound is formed. Which statement is correct?

(a) Equal masses of the elements must be used. (b) The compound shows similar chemical properties to those of the elements. (c) The elements must both be non-metals. (d) When the elements react together covalent compounds form.

(45) The empirical formula of a liquid compound is C2H4O. To find the empirical formula, it

is necessary to know (a) The density of the compound. (b) The percentage composition by mass of the compound. (c) The relative molecular mass of the compound. (d) The volume occupied by 1 mole of the compound.

(46) 25.0 g of hydrated copper (II) sulphate crystals are heated to produce anhydrous copper (II) sulphate and water vapour.

CuSO4.5H2O(s) → CuSO4(s) + 5H2O(g) What is the mass of anhydrous copper (II) sulphate formed? [Mr: CuSO4=160; H2O=18] (a) 9.0 g (b) 16.0 g

(c) 22.5 g (d) 25.0 g

(47) Which reagent can be used to react with dilute hydrochloric acid to prepare silver chloride?

(a) Aqueous silver nitrate (b) Solid silver

(c) Solid silver carbonate (d) Solid silver oxide

(48) What is removed or destroyed when water is desalinated to make it drinkable?

(a) Bad odours (b) Harmful bacteria

(c) Sodium chloride (d) Solid particles

(49) A substance dissolves in water to form a colourless solution. This solution reacts with aqueous silver nitrate in the presence of dilute nitric acid to give a yellow precipitate. What is the possible identity of the substance?

(a) Calcium iodide (b) Copper(II) chloride (c) Iron(II) iodide (d) Sodium chloride

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(50) Which substance has a giant covalent structure at room temperature?

(a) Methane (b) Sand

(c) Sodium chloride (d) Water

(51) Pollutant gases are released by the bacterial decay of vegetable matter. The bacterial decay of vegetable matter is the main source of which gas?

(a) Carbon monoxide (b) Methane

(c) Nitrogen dioxide (d) Sulphur dioxide

(52) Aluminium vessels should not be washed with materials containing washing soda

since. (a) Washing soda is expensive (b) Washing soda is easily decomposed (c) Washing soda reacts with aluminium to form soluble aluminate (d) Washing soda reacts with aluminium to form insoluble aluminium oxide

(53) Copper element occurs mainly in two isotopes: Cu-63 and Cu-65. The following figure illustrates the composition of the sample taken from the copper coin.

From the above figure, what are the correct percentages of the isotopes?

(a) Cu-63 = 65% and Cu-65 = 35% (b) Cu-63 = 63% and Cu-65 = 37% (c) Cu-63 = 70% and Cu-65 = 30% (d) Cu-63 = 30 % and Cu-65 = 70%

(54) X is a Group I metal. Y and Z are Group VII elements. When X reacts with Y a salt is formed. Z has the ability to displace the anion in the formed salt to form a different

salt. What are X, Y and Z?

X Y Z

(a) K Cl2 I2

(b) Li Cl2 Br2

(c) K Br2 Cl2

(d) Na F2 Cl2

(55) Four substances have the physical properties shown. Which substance is an ionic

solid?

Melting Point (oC)

Boiling Point (oC)

Electrical conductivity

of solid

Electrical conductivity of

molten substance

Electrical conductivity of

aqueous solution

(a) -115 -85 Poor Poor Good

(b) 660 2470 Good Good Insoluble

(c) 993 1695 Poor Good Good

(d) 1610 2230 Poor Poor Insoluble

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PART B [65 marks]

Question 1 (5 marks)

The electronic configurations of other five atoms are shown.

A B C D E

Which electronic configuration represents each of the following descriptions? [In this question, each electronic configuration may be used once, more than once or not at all].

(a) A sodium atom (1 mark) (b) An atom of a reactive non-metallic element (1 mark)

(c) An atom with a proton (atomic) number of 12 (1 mark) (d) An atom of a noble gas found in period 2. (1 mark) (e) An atom which forms a noble gas electronic configuration when it gains two electrons.

(1 mark)


The alkanes are a homologous series of saturated hydrocarbons. (a) What is the meaning of the term saturated? (1 mark) (b) Write the general formula for the alkane homologous series. (1 mark) (c) Each member of a particular homologous series has the same general formula. Give one other

characteristic of a homologous series. (1 mark) (d) Construct the equation for the complete combustion of pentane, C5H12. (2 marks) (e) Draw the structure of a branched alkane with the formula C5H12. Show all of the atoms and all

of the bonds. (1 mark) (f) Chlorine reacts with pentane: C5H12 + Cl2 → C5H11Cl + HCl

(i) What name is given to this type of chemical reaction? (1 mark) (ii) What essential condition is needed for chlorine to react with pentane? (1 mark)

(g) Propene can be obtained by cracking of alkanes. (i) Write an equation for the thermal cracking of one molecule of C10H22 to give one molecule of

propene (CH3CH=CH2) and one molecule of an alkane only. (1 mark) (ii) State one reason why cracking is important. (1 mark)


The Periodic Table is an arrangement of elements in groups and periods. (a) Describe how the position of an element in the Periodic Table is related to its electronic

configuration. (2 marks) (b) Aluminium is an element in Group III of the Periodic Table. Deduce the electronic configuration

of the aluminium ion. (1 mark) (c) Aluminium reacts with oxygen to form aluminium oxide, Al2O3.

(i) Construct the equation for this reaction. (1 mark) (ii) Aluminium oxide reacts with both acids and alkalis. Name the type of oxide which reacts

with both acids and alkalis. (1 mark) (d) The element germanium has five naturally occurring isotopes. An isotope of germanium is

represented by the symbol shown.

(i) What is the meaning of the term isotopes? (2 marks) (ii) Deduce the number of neutrons in one atom of this isotope of germanium. (1 mark)

(e) The formula of cerium carbonate is Ce2(CO3)3. Calculate the percentage by mass of cerium in cerium carbonate. Use the Periodic Table to answer. (2 marks)

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This question is about covalent and ionic compounds. (a) Covalent compounds such as H2S have low melting points and do not conduct electricity when

molten. Draw one line from each property to the explanation of the property. (2 marks) PROPERTY EXPLANATION OF PROPERTY

Electrons are free to move

Low boiling point There are no charged particles free to move

Ions are free to move

Weak intermolecular forces of attraction

Does not conduct electricity when molten

Bonds are weak

Bonds are strong

(b) Ionic compounds such as K2S have high boiling points and conduct electricity when dissolved in

water. Draw one line from each property to the explanation of the property. (2 marks) PROPERTY EXPLANATION OF PROPERTY

Electrons are free to move

High boiling point There are no charged particles free to move

Ions are free to move

Weak intermolecular forces of attraction

Conduct electricity when molten

Bonds are weak

Bonds are strong

(c) Oxygen reacts with hydrogen to form water. Sulphur reacts with hydrogen to form hydrogen sulphide (H2S). Some properties of hydrogen sulphide are listed.

It is a gas at room temperature. It reacts with aqueous sodium hydroxide. It is a reducing agent. It burns in air.

Describe three ways in which the properties of water differ from those of H2S. (3 marks)

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(d) Use a table to classify the following compounds into ionic and covalent (compounds) from the bubbles below. (3 marks)


(a) Solid P is a mixture of two compounds. The two compounds contain the same cation but different anions. An excess of dilute hydrochloric acid (HCl) is added to P. Bubbles of carbon dioxide gas are given off and the solid dissolves completely, forming a colourless solution. (i) What conclusion can be made from the fact that the solution is colourless? (1 mark) (ii) Identify the anion which reacts with HCl to produce carbon dioxide gas. (1 mark)

(b) Solid Q is a mixture of two compounds. The compounds each contain a different cation but the same anion. Copy and complete the table. (8 marks)

[Any gases given off should be named and identified by a suitable test and observation].

TEST OBSERVATION CONCLUSION

(a)

Q is dissolved in water The solution is divided into three parts for tests (b), (c), and (d).

A colourless solution is formed.

(b)

(i) To the first part. Aqueous sodium hydroxide is added until a change is seen.

(ii) An excess of aqueous sodium hydroxide is added to the mixture from (i).

(iii) The mixture from (ii) is warmed.

Q may contain Al3+, Ca2+ or Zn2+ ions. Q contains Al3+ or Zn2+ ions. Q contains NH4

+ ions

(c)

(i) To the second part, aqueous ammonia is added until a change is seen.

(ii) An excess of aqueous ammonia is added to the mixture from (i)

Q may contain Al3+ or Zn2+ ions. Q contains Zn2+ ions.

(d)

Q contains Cl- ions.


Sodium carbonate reacts with dilute hydrochloric acid: Na2CO3 + 2HCl → 2NaCl + H2O + CO2

A student investigated the volume of carbon dioxide produced when different masses of sodium carbonate were reacted with dilute hydrochloric acid. This is the method used.

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1. Place a known mass of sodium carbonate in a conical flask. 2. Measure 10 cm3 of dilute hydrochloric acid using a measuring cylinder. 3. Pour the acid into the conical flask. 4. Place a bung in the flask and collect the gas until the reaction is complete.

The student set up the apparatus as shown in figure below.

(a) Identify the error in the way the student set up the apparatus. (1 mark) (b) Describe what would happen if the student used the apparatus shown. (1 mark) (c) The student corrected the error.

The student’s results are shown in the table below.

Mass of sodium carbonate (in g) Volume of carbon dioxide gas (in cm3)

0.07 16.0

0.12 27.5

0.23 52.0

0.29 12.5

0.34 77.0

0.54 95.0

0.59 95.0

0.65 95.0

(i) The result for 0.29 g of sodium carbonate is anomalous. Suggest what may have happened

to cause this anomalous result. (1 mark) (ii) Why does the volume of carbon dioxide collected stop increasing at 95.0 cm3? (1 mark) (iii) What further work could the student do to be more certain about the minimum mass of

sodium carbonate needed to produce 95.0 cm3 of carbon dioxide? (1 mark) (iv) The carbon dioxide was collected at room temperature and pressure (RTP). The volume of

one mole of any gas at room temperature and pressure is 24.0 dm3. How many moles of carbon dioxide is 95.0 cm3? (2 marks)

(v) Suggest one improvement that could be made to the apparatus used that would give more accurate results. Give a reason for your answer. (2 marks)

(vi) One student said that the results of the experiment were wrong because the first few

bubbles of gas collected were air. A second student said this would make no difference to the results. Explain why the second student was correct. (1 mark)


(a) Three gases A, B and C have the properties shown in the table.

Gas Density Solubility In water Appearance

A More dense than air Soluble Colourless

B Less dense than air Soluble Brown

C More dense than air Insoluble Colourless

Some apparatus used to collect gases is shown.

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Which apparatus, X, Y or Z, is most suitable to collect each gas? (i) Gas A (0.5 mark) (ii) Gas B (0.5 mark)

(b) Gas C can be collected using apparatus Z. (i) State why apparatus Z is more suitable than apparatus Y to collect gas C. (1 mark) (ii) State why apparatus Z is more suitable than apparatus X to collect gas C. (1 mark)

(c) A student adds magnesium ribbon to dilute hydrochloric acid and the temperature of the dilute hydrochloric acid changes. The diagrams below show parts of the thermometer stem giving the temperatures of the dilute hydrochloric acid both before and after the addition of magnesium ribbon.

Initial

temperature

Final

temperature

(i) A gas is produced during the reaction. Name this gas. Give a test and observation to identify the gas. (2 marks)

(ii) Construct the equation for the reaction between magnesium and dilute hydrochloric acid. (1 mark)

(iii) Copy and complete the following table and calculate the change in temperature. (3 marks)

Final temperature of the acid (oC)

Initial temperature of the acid (oC)

Change in temperature (oC)

(iv) What type of reaction does this temperature change indicate? (1 mark)

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