Chemistry – Form 4 Secondary – Track 2 – 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 4 CHEMISTRY TIME: 1h 30min

Name: _________________________

Class: _________________________

Useful Data: Atomic numbers and relative atomic masses are shown in the periodic table

printed on a separate page.

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

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 2

Page 2 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

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

1 Choose an element from the following list which best fits the descriptions:

helium, iron, zinc, copper, nitrogen, bromine, sulfur, calcium.

Each element may be used once, more than once or not at all.

a) A diatomic gas common in the

earth’s atmosphere.

___________________________________________________________________ [1]

b) Forms rhombic and monoclinic crystals.

___________________________________________________________________ [1]

c) Used to galvanize iron doors etc.

___________________________________________________________________ [1]

d) The only liquid non-metal at room temperature.

___________________________________________________________________ [1]

e) A very light monoatomic gas.

___________________________________________________________________ [1]

f) An element found in ammonia.

___________________________________________________________________ [1]

g) The main constituent in human bones.

___________________________________________________________________ [1]

h) An inert gas.

___________________________________________________________________ [1]

i) This non-metal is displaced when chlorine gas is bubbled through a solution of its

salt.

___________________________________________________________________ [1]

j) Purified by electrolysis.

___________________________________________________________________ [1]

Chemistry – Form 4 Secondary – Track 2 – 2016 Page 3 of 12

2 Some copper(II) sulfate crystals were dissolved in

water and electrolysed using inert graphite electrodes

for 10 minutes.

a) Draw a labelled diagram of the apparatus which could be used for this experiment.

[4]

b) During the experiment bubbles of a gas were produced and collected.

State two other changes which would be observed during the experiment.

___________________________________________________________________

___________________________________________________________________

[2]

c) The gas produced was colourless and odourless. Name the gas and give a chemical

test for it.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

[2]

d) The current used during the experiment was 0.02A. Calculate the charge used

during the experiment.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

[2]

Page 4 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

3 Sulfur is a yellow non-metal found in group 6 of the periodic table. It is a useful and

important element but when burnt in air, it can be a source of pollution.

a) Write a balanced chemical equation for the combustion of sulfur in oxygen.

Include state symbols.

___________________________________________________________________ [3]

b) The product of the above reaction goes on to react with water vapour and oxygen

in air to produce a strong acid. Name this acid and also the type of pollution it

causes.

___________________________________________________________________

___________________________________________________________________

[2]

c) The product of reaction a) is also used in industry to manufacture an acid. The

process involves three stages and the second stage requires specific conditions.

i) Name the process.

_______________________________________________________________

[1]

ii) Name the catalyst used for the second stage of the process and state the

temperature at which this reaction operates.

_______________________________________________________________

_______________________________________________________________

[2]

iii) The acidic product is then reacted with ammonia to produce artificial fertiliser.

Write a balanced chemical equation for this reaction.

_______________________________________________________________

[2]

Chemistry – Form 4 Secondary – Track 2 – 2016 Page 5 of 12

4 Last summer, James was

watching a fireworks display

and he started wondering

where the colours in the sky

were coming from.

Fireworks displays involve the

burning of metal compounds.

a) Which metal compounds could be used to give the following colours:

i) Lilac: __________________________________________________________ [1]

ii) Golden yellow: __________________________________________________ [1]

b) By accident, one of the fireworks did not burn properly and some of its chemicals

fell into a pool of water. James was nearby and he collected some of the water for

further testing in the lab.

i) James decided to add acidified barium chloride to a sample of the water. A

white precipitate formed. Which ion was present in his sample?

_______________________________________________________________

[1]

ii) Write a balanced ionic equation for the reaction taking place.

_______________________________________________________________

[2]

iii) Another sample of the solution produced ammonia gas when it was heated

with some aluminium turnings and NaOH solution. Which ion was present?

_______________________________________________________________

[1]

c) James performed another chemical test where he added a solution of sodium

hydroxide to another sample of the water collected. A blue precipitate was formed

which was insoluble in excess sodium hydroxide solution.

i) Name the ion present.

_______________________________________________________________

[1]

ii) Write a balanced ionic equation for the reaction taking place.

_______________________________________________________________

[2]

iii) Name the section of the periodic table where this ion is found.

_______________________________________________________________

[1]

Page 6 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

5 The chemical reaction between sulfuric

acid and sodium carbonate is known to

produce carbon dioxide.

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

___________________________________________________________________

[3]

b) In this reaction 24.7 cm3 of 0.2 mol dm

-3 H2SO4 was added to the carbonate until the

solution stopped fizzing.

i) Calculate the number of moles of acid added.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[3]

ii) From your equation, calculate the number of moles of sodium carbonate

which reacted with the acid.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[2]

iii) Given that 1 mole of sodium carbonate weighs 106 g, calculate the mass of

sodium carbonate which was originally present in the flask.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[2]

Chemistry – Form 4 Secondary – Track 2 – 2016 Page 7 of 12

6 Aluminium is one of the metals routinely recycled in Malta. This is very important to us

as aluminium has many uses.

a) Mention two uses of aluminium.

___________________________________________________________________

___________________________________________________________________

[2]

b) Aluminium oxide reacts with both acids and alkalis. What is the name given to such

oxides?

___________________________________________________________________

[1]

c) The extraction of

aluminium involves

digging up the material

from the Earth creating

huge scars. The material

is then purified and

electrolysed.

i) Name the raw material used in this process.

_______________________________________________________________

[1]

ii) What gas is initially produced in this process ?

_______________________________________________________________

[1]

iii) The gas mentioned in c) ii) reacts with the anode used in industry to form

another gas. What is the name of this gas?

_______________________________________________________________

[1]

iv) When molten, the ions in aluminium oxide move freely in the liquid.

Al2O3 → 2Al

3+ + 3O

2-

Write ionic half equations to show how pure aluminium and oxygen are

produced.

_______________________________________________________________

_______________________________________________________________

[4]

Page 8 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

SECTION B – Answer TWO questions only. This section carries 40 marks.

7 Chlorine is a non-metal which is found in group 7 of the periodic table.

a) What type of bond exists between the atoms in a chlorine molecule?

__________________________________________________________________

[2]

b) What is the colour and physical state of chlorine at room temperature and pressure?

__________________________________________________________________

[2]

c) How many electrons are present in the outer shell of a chlorine atom and what is its

most common oxidation?

__________________________________________________________________

[2]

d) Write the electronic configuration of an atom of chlorine.

__________________________________________________________________

[2]

e) Chlorine is a strong oxidizing agent. When it is bubbled through a solution of some

halide salts it displaces the halide ion.

i) Complete the equation by inserting the appropriate state symbols:

Cl2 ( ) + NaI ( ) ⟶ NaCl ( ) + I2 (aq)

[3]

ii) From the equation state whether chlorine is gaining or losing electrons.

______________________________________________________________

[2]

f) Mention two uses of chlorine.

___________________________________________________________________

___________________________________________________________________

[2]

g) In the lab chlorine can be produced by the oxidation of hydrochloric acid.

The equation for the reaction is:

MnO2(s) + 4HCl(aq) ⟶ MnCl2(aq) + 2H2O(l) + Cl2(g)

i) Use the equation to label the diagram appropriately. [3]

ii) State and explain one safety precaution to be observed during this experiment.

________________________________________________________________

[2]

Chemistry – Form 4 Secondary – Track 2 – 2016 Page 9 of 12

8 Ammonia can be produced on a small scale in the laboratory or on a large scale in

industry. The reactions are very different from each other.

a) To produce ammonia in the laboratory a compound such as ammonium chloride is

heated in the presence of calcium hydroxide.

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

_______________________________________________________________

[3]

ii) Give two physical properties of the ammonia gas produced.

_______________________________________________________________

_______________________________________________________________

[2]

b) The apparatus below can be used to produce and collect a dry sample of the ammonia

gas.

i) Label the diagram appropriately. [4]

ii) Name and draw another piece of apparatus which can be used to collect the

ammonia instead of the gas jar.

________________________________________________________________

[2]

Page 10 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

8

c) In industry nitrogen gas is combined with hydrogen gas under certain conditions to

produce ammonia.

i) Name the industrial process.

_______________________________________________________________

[1]

ii) Write a balanced chemical equation of this reaction. Include all state symbols.

_______________________________________________________________

[3]

iii) Give the three essential conditions for this reaction to occur at a reasonable

rate.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[3]

d) Ammonia is one of the gases being used to replace chlorofluorocarbons (CFCs) in

refrigeration. CFCs cause aerial pollution by reacting and removing a protective gas

from the upper atmosphere thus allowing more UV rays to reach the Earth’s surface.

i) Which gas present in the upper levels of the Earth’s atmosphere is being

reduced by CFCs?

_______________________________________________________________

[1]

ii) Name the disease mostly associated with increased levels of UV rays.

_______________________________________________________________

[1]

Chemistry – Form 4 Secondary – Track 2 – 2016 Page 11 of 12

9 An experiment was carried out to find the percentage content of calcium carbonate in

limestone. The experiment was done in two parts:

Part 1.

5 g of dry limestone were weighed accurately in a large beaker, then 50 cm3 of

2 mol dm-3

HCl were added. Carbon dioxide was produced when the HCl reacted

with the limestone but some of the HCl remained in excess.

Part 2.

The excess HCl was then titrated against 0.1 mol dm-3

NaOH. The titre value was

22.7 cm3.

a) i) In the second part of the experiment 22.7 cm3 of 0.1 mol dm

-3 NaOH were

used. Find the number of moles of NaOH which reacted in Part 2.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[2]

ii) Write a balanced chemical equation for the reaction between HCl and NaOH.

Include all state symbols.

_______________________________________________________________

[3]

iii) From the ratio of acid and alkali given by the above reaction find the number

of moles of acid which were in excess (did not react with the calcium

carbonate).

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[3]

Page 12 of 12 Chemistry – Form 4 Secondary – Track 2 – 2016

b) i) The hydrochloric acid and calcium carbonate react according to the following

equation. Complete the equation by filling in the missing information.

CaCO__ (s) + __HCl( __ ) ⟶ CaCl__ ( __ ) + H2O( __ ) + CO2(g)

[3]

9 b) ii) Calculate the amount of HCl in moles present in 50 cm3 of 2 mol dm

-3 HCl

that were used in Part 1 of the experiment.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

[2]

iii) Calculate the number of moles of HCl which reacted with CaCO3 by

subtracting the number of moles of HCl which were in excess in a) iii) from

the original amount of acid in b) ii).

_______________________________________________________________

[2]

iv) Using the equation in b) i) find the number of moles of calcium carbonate

which reacted with the acid.

_______________________________________________________________

_______________________________________________________________

[2]

v) If one mole of CaCO3 weighs 100 g, calculate the mass of CaCO3 that reacted

with the acid.

_______________________________________________________________

_______________________________________________________________

[2]

vi) The mass of CaCO3 found in b) v) was present in 5 g of limestone. Find the

percentage CaCO3 present in limestone.

_______________________________________________________________

_______________________________________________________________

[2]

End of paper.