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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.
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