Chemistry – Form 5 Secondary – Track 3 – 2016 Page 1 of 12

DIRECTORATE FOR QUALITY AND STANDARDS IN EDUCATION

Department of Curriculum Management

Educational Assessment Unit

Annual Examinations for Secondary Schools 2016

FORM 5 CHEMISTRY TIME: 1h 45min

Name: _________________________ Class: _______________

Useful Data Atomic numbers and relative atomic masses are shown in the periodic table printed below.

One mole of any gas occupies 22.4 dm3 at standard temperature (0 °C / 273 K) and

pressure (1 atm. / 760 mmHg).

Faraday constant = 96500 C mol-1

Q = It

PERIODIC TABLE

1 2 3 4 5 6 7 0

1

1H

4

2He

7

3Li

9

4Be

11

5B

12

6C

14

7N

16

8O

19

9F

20

10Ne

23

11Na

24

12

Mg

27

13Al

28

14Si

31

15P

32

16S

5.35

17Cl

40

18Ar

39

19K

40

20Ca

45

21Sc

48

22Ti

51

23V

52

24Cr

55

25Mn

56

26Fe

59

27Co

59

28Ni

5.63

29Cu

65

30Zn

70

31Ga

73

32Ge

75

33As

79

34Se

80

35Br

84

36Kr

85

37Rb

88

38Sr

89

39Y

91

40Zr

93

41Nb

96

42Mo

99

43Tc

101

44Ru

103

45Rh

106

46Pd

108

47

Ag 112

48Cd

115

49In

119

50Sn

122

51Sb

128

52Te

23

11Na

127

53I

23

11Na

131

54Xe

133

55Cs

223

87Fr

137

56Ba

139

57La

178

72Hf

181

73Ta

184

74W

186

75Re

190

76O s

192

77Ir

195

78Pt

197

79Au

201

80

Hg 204

81Tl

207

82Pb

209

83Bi

210

84Po

210

85At

222

86Rn

Key: a

bX

relative atomic mass

symbol atomic number

Marks Grid [ For Examiner’s use only ]

Question

No.

Section A Section B

1 2 3 4 5 6 7 8 9

Max

Mark 10 10 10 10 10 10 20 20 20

Theory

Total

Actual

Mark

Theory Paper: 85% Practical: 15% Final Score: 100%

Track 3

Page 2 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

SECTION A – Answer ALL questions. This section carries 60 marks.

1 Earth’s atmosphere is made up of a mixture of gases.

a) Name the two most abundant gases in Earth’s atmosphere.

_____________________________________________________________________ 1

b) Give the percentage amount for each of the gases mentioned above.

_____________________________________________________________________ 1

c) Describe, in terms of the kinetic theory of matter, the behaviour of particles in a gas.

_____________________________________________________________________

_____________________________________________________________________

2

d) Carbon dioxide is a gas that is found in Earth’s atmosphere. Draw a dot cross

diagram of a molecule of carbon dioxide showing outer shells only.

3

e) What is the name of the type of bond present in carbon dioxide?

_____________________________________________________________________ 1

f) A component of the Earth’s atmosphere is made of elements that do not form

molecules. Name one of these elements.

_____________________________________________________________________ 1

g) Name the process by which the gases present in air can be separated from each other.

_____________________________________________________________________ 1

Chemistry – Form 5 Secondary – Track 3 – 2016 Page 3 of 12

2 Sea water is a solution of many salts dissolved in water. The main salt present in sea

water is sodium chloride, NaCl. When sea water evaporates, crystals of NaCl form.

a) In humid conditions NaCl crystals absorb water vapour from the air and dissolve to

form a concentrated solution. What is the name of this process?

_____________________________________________________________________ 1

b) Sea water is not suitable to drink. Describe how fresh water can be obtained from sea

water by reverse osmosis.

_____________________________________________________________________

_____________________________________________________________________

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3

c) The graph below shows the solubility of sodium chloride against temperature

.

i) How much NaCl, in grams, is required to produce a saturated solution at 90 °C

if 1000 g of water are used? ________________________________________

2

ii) What would happen if a saturated solution at 90 °C is allowed to cool to room

temperature?

________________________________________________________________ 1

d) Draw a dot cross diagram of sodium chloride.

3

Solu

bil

ity –

gra

m N

aCl

100 g

H20

Temperature (°C)

Page 4 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

3 Acids are a group of substances that have similar chemical properties. They react with

many materials and are corrosive. Hydrochloric acid is an example of a mineral acid.

a) For each of the materials below, write a balanced chemical equation to show what

happens when the material and hydrochloric acid are mixed together.

i) calcium oxide

________________________________________________________________ 2

ii) sodium carbonate

________________________________________________________________ 2

b) When acids react with metals such as magnesium, hydrogen gas is generated. Draw a

diagram of the apparatus in the space provided below, to show how hydrogen gas can

be produced and collected in the lab.

3

c) Describe how hydrogen gas can be tested and state the expected result for this test.

_____________________________________________________________________

_____________________________________________________________________

1

d) Most crops prefer soil conditions that are not too acidic. A farmer needs to have his

field checked before he plants it. He needs it to be at a pH of around 7.

i) What would you do to check that the soil has an acceptable pH value?

________________________________________________________________

________________________________________________________________

1

ii) If the above test shows that the field is too acidic, what should the farmer do to

neutralise the acidity in the soil?

________________________________________________________________

________________________________________________________________

1

Chemistry – Form 5 Secondary – Track 3 – 2016 Page 5 of 12

4 Sodium bromide (NaBr) is a salt that does not conduct electricity when it is in the solid

state. However, it conducts electricity either when molten or when dissolved in water.

a) Explain why NaBr does not conduct electricity when it is in the solid state.

_____________________________________________________________________ 1

If NaBr is in the liquid state, it will conduct a current of electricity and decompose. The

diagram below shows the setup that would be used.

b) Name the substance formed at the cathode.

_____________________________________________________________________ 1

c) Write the half equation that happens at the anode.

_____________________________________________________________________ 2

The electrolysis of NaBr is a redox reaction.

d) In the electrolytic cell, does oxidation happen at the cathode or the anode?

_____________________________________________________________________ 1

e) Explain, in terms of electrons, what happens at the cathode.

_____________________________________________________________________ 1

When NaBr is dissolved in water to make a very dilute solution, it will also conduct a

current of electricity.

f) Name the substance formed at the anode, giving a reason for your answer.

_____________________________________________________________________

_____________________________________________________________________

2

g) Write the half equation that happens at the cathode.

_____________________________________________________________________ 2

Page 6 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

5 During an experiment to identify two white crystalline substances, a student noted the

following observations:

a) When substance A was heated in a blue Bunsen flame, using a nichrome wire, a lilac

colour was observed.

When a sample of substance A was dissolved in distilled water and mixed with

acidified silver nitrate solution a cream precipitate was formed. On mixing another

sample of substance A with lead(II) nitrate, a canary yellow precipitate formed.

Substance A is: ________________________________________________________

2

b) When a solution of substance B was mixed with a solution of sodium hydroxide, a

white precipitate was obtained. A flame test gave a brick red colour.

When dilute hydrochloric acid was added to a sample of substance B, a gas that

smells of burning sulfur was produced. Furthermore, a solution of substance B

decolorizes aqueous potassium permanganate.

Substance B is: ________________________________________________________

2

During another experiment to determine the concentration of a solution of sodium

hydroxide, another student decided to perform a titration.

c) The diagrams show two items of the equipment needed to perform a titration. Label

the diagrams in the spaces provided.

1

d) 25 cm3 of sulfuric acid solution whose concentration was 1 mol dm

-3 was used to

neutralise the alkali.

i) Write a balanced chemical equation for the reaction that happens between

sulfuric acid and sodium hydroxide. Do not include state symbols.

________________________________________________________________ 2

ii) After performing the titration, the average titre value of sodium hydroxide was

found to be 20.5 cm3. Calculate the concentration of this solution.

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

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3

Chemistry – Form 5 Secondary – Track 3 – 2016 Page 7 of 12

6 The laboratory preparation of ammonia involves mixing and heating two solid substances,

ammonium chloride and calcium hydroxide.

a) Write a balanced chemical equation including state symbols for this reaction.

_____________________________________________________________________ 3

b) The following diagram is a typical setup that is used in the laboratory for the

preparation of ammonia.

i) The diagram shows ammonia being collected in a particular way. What is the

name of this technique?

________________________________________________________________ 1

ii) Why is ammonia collected in this manner?

________________________________________________________________ 1

iii) The drying agent used is calcium oxide. Can any drying agent be used to dry

ammonia? Explain your reasoning.

________________________________________________________________ 2

c) Provided that 5 g of ammonium chloride reacted with excess calcium hydroxide,

calculate the volume of ammonia, in dm3, that would be produced at STP.

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

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3

Page 8 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

SECTION B – Answer TWO questions only on the foolscaps provided.

This section carries 40 marks.

7 Ethanol can be obtained either naturally or synthetically.

a) Draw the display formula of ethanol showing all bonds. 1

b) What is the name of the homologous series which ethanol is a member of? 1

c) Write the general formula of the homologous series mentioned above. 1

d) Give the name of another member of this homologous series which has 4 carbon

atoms.

1

Ethanol is a basic material in all alcoholic beverages (drinks) where it is produced

naturally. 93% of the world’s ethanol is produced by this natural process.

e) What is the name of the natural process that produces ethanol? 1

f) Using a labelled diagram, briefly describe how this natural process can be performed

in a laboratory.

5

7% of the world’s ethanol production is produced synthetically. It is an important

substance because it has many uses.

g) Apart from the use in beverages, mention two uses of ethanol. 2

h) Write a balanced chemical equation including state symbols for the synthetic

production of ethanol.

3

The synthetic production of ethanol is a chemical process which reaches equilibrium.

Phosphoric acid embedded in silica, a temperature of 300 °C and a pressure of 60

atmospheres are used to increase the yield of ethanol.

i) What is the function of phosphoric acid and why is it used? 2

j) What does the phrase “increase the yield of ethanol” mean? 1

k) Explain why a pressure of 60 atm. is required to increase the yield of ethanol. 2

Please turn the page.

Chemistry – Form 5 Secondary – Track 3 – 2016 Page 9 of 12

8 The Haber process was invented in 1905 by Fritz Haber to solve

the problem of the lack of reactivity of nitrogen to produce

nitrogenous compounds such as ammonia and nitrates.

The process involves reacting nitrogen (obtained from the

fractional distillation of liquid air) and hydrogen (obtained from

steam reforming) to form ammonia in liquid form. Ammonia is

then easily converted into other nitrogenous compounds which

are used mainly in the production of fertilizers and explosives.

a) Why do you think that nitrogen is so unreactive? 1

b) Write a balanced chemical equation, including state symbols, for the production of

ammonia by the Haber process.

3

c) This process is one that requires special conditions. List these conditions with respect

to the catalyst used, temperature and pressure.

3

d) The catalyst used is usually in a finely divided state. Why do you think that the

catalyst needs to be like this? Explain your reasoning in terms of the collision theory.

3

e) Would the use of a catalyst affect the equilibrium position? Explain. 3

f) What would happen to the amount of ammonia produced if the pressure on the system

increases? Explain your answer in terms of Le Chatelier’s principle.

3

g) Apart from using temperature or pressure to change the equilibrium position, what

can be done to increase the production of ammonia? Explain your answer in terms of

equilibrium position and state how this can be achieved.

3

h) Comment on the rate of reaction of the forward and backward reactions when this

system is in equilibrium.

1

Page 10 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

9 During an experiment to investigate the effect of surface area on the rate of chemical

reactions of heterogeneous reactions, a student decided to react calcium carbonate chips

with hydrochloric acid. The following table shows the data of the student’s experiment.

Time / min 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Volume of CO2 gas / cm3 0 15 24 28 31 33 35 35 35

a) Plot a graph of volume of CO2 against time and label it X. 5

b) At which point on the graph would you say that the reaction came to an end? 1

c) When was the rate of reaction at its lowest? 1

d) From your graph, determine:

i) the time at which the volume of CO2 reached 30 cm3. 1

ii) the volume of CO2 that was collected at 0.8 minutes. 1

e) Why is this reaction classified as a heterogeneous reaction? 1

f) Write a balanced chemical equation for this reaction. Include state symbols. 3

g) If the reagent bottle holding the acid was to be placed in a refrigerator, its temperature

would be lowered from room temperature to 4 °C. Given that everything else

remained the same, draw a sketch labelled Y, on the graph plotted in a), to show the

rate curve you would expect.

2

h) Explain, in terms of the collision theory, how changing the temperature of the acid

affects the rate of the chemical reaction.

2

The student repeated the experiment with the same amount of calcium carbonate and

hydrochloric acid. But this time round, the student crushed the calcium carbonate chips

into smaller pieces.

i) On your graph plotted in a), draw a sketch labelled Z, to show the graph expected

when the surface area of the calcium carbonate changes.

1

j) Explain, in terms of the collision theory, how changing the surface area of calcium

carbonate affects the rate of the chemical reaction.

2

Chemistry – Form 5 Secondary – Track 3 – 2016 Page 11 of 12

Page 12 of 12 Chemistry – Form 5 Secondary – Track 3 – 2016

End of paper.