Section A (Answer ALL questions.)
1.
For each of the tasks listed in the table below, decide which substance on the right is the
best to use to accomplish the task. Explain your answer in each case.
Task
Substances
(a) To attach a substance to the iron hull of a
calcium,
tanker to prevent the hull from rusting
copper,
zinc
(b)
To make the body of an aircraft
(c)
To make feeding bottles for babies
aluminium,
duralumin,
stainless steel
polyethene,
polystyrene,
urea-methanal
(9 marks)
1.
2.
2.
For each of the following, award 1 mark for the correct choice and 2 marks for the
explanation; disregard the explanation for a wrong choice.
(a) zinc
both zinc and calcium are stronger reducing agent/more reactive than
iron/occupy higher positions in the electrochemical series/can prevent iron
from rusting by sacrificial protection
or, copper is weaker reducing agent/less reactive than iron. It cannot prevent
iron from rusting
Calcium reacts readily with water
(b) duralumin
Stainless steel has the highest density/is too heavy for making aircraft
or, duralumin is lighter than stainless steel/has a lower density than stainless
steel
duralumin is more corrosion resistant/(mechanically) stronger than
aluminium
(c) polystyrene
Feeding bottles are usually sterilized by heating in boiling water, polyethene
has a low m.p./cannot withstand the temperature of boiling water/deforms at
the temperature of boiling water
Urea-methanal. It cannot be moulded into the shape of a bottle/is not
transparent
(DO NOT accept urea-methanal is a thermosetting plastic alone.
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(a)
Aspirin is a painkiller, but it may cause damage to the stomach lining of the user.
(i) What is the active ingredient in aspirin?
(ii) Some people who suffer from stomach disturbance take an anti-acid whenever
they take aspirin. Name ONE chemical which is used as an active ingredient in
anti-acids.
(b)
Codeine is one of the drugs abused by some teenagers in Hong Kong.
(i) State ONE medicinal use of codeine.
(ii) State ONE adverse side effect of taking codeine.
(iii) State ONE measure taken by Hong Kong Government to prevent teenagers
from abusing codeine.
(5 marks)
(a)
(i)
(ii)
(b)
(i)
(ii)
acetylsalicylic acid/sodium acetylsalicylate/acetylsalicylate
†magnesium hydroxide/aluminium hydroxide/calcium hydroxide/
sodium hydrogencarbonate/magnesium carbonate/calcium carbonate/
magnesium trisilicate
cough suppressant/in cough mixture/pain relief/reduce activity of
nervous system
codeine may cause drowsiness/addiction
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(iii) legislation: consumers can purchase codeine containing cough
mixture from drug stores only if he can produce a doctor's
prescription
or, education: teach the public the danger of codeine abuse
3.
(a)
(b)
(c)
3.
(a)
(b)
(c)
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Suggest ONE method to determine the pH of an aqueous solution.
Arrange the following substances in the order of increasing pH and explain your
answer.
1 M ethanoic acid, 1 M hydrochloric acid, 1 M sulphuric acid
Three solution samples, A, B and C, are being tested for the purpose of perming hair.
The table below lists the pH of these samples:
Sample
pH
A
6.5
B
8.5
C
10.0
Which sample is most suitable for perming hair? Explain your answer.
(6 marks)
Using pH paper/universal indicator/pH paper
pH: 1 M sulphuric acid < 1 M hydrochloric acid < 1 M ethanoic acid
ethanoic acid is a weak acid/undergoes incomplete ionization ∴ it has the
highest pH
or, both hydrochloric acid and sulphuric acid are strong acids/undergo
complete ionization
sulphuric acid is dibasic while hydrochloric acid is monobasic ∴ 1 M
H 2SO 4 contains a higher concentration of H  (aq ) ions than 1 M HCl
(1 mark for the correct order; 2 marks for the explanation. The order and the
explanation should be marked separately.)
B because it is alkaline. Solution C has a pH which is too high and may
cause the hair to look duller/feel coarser/break more easily.
or, C because it is alkaline. The higher pH of C will make the curls more
permanent
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For questions 4 and 5, candidates are required to give paragraph-length answers. 3 of the
marks for each of these two questions will be awarded for the effective communication of
knowledge in Chemistry.
4.
Briefly describe how you would conduct an experiment, using the materials and apparatus
listed below, to nickel-plate a clean metal spoon. (Diagrams are NOT required.) State the
expected observation of the experiment.
A clean metal spoon, a nickel plate, nickel(II) sulphate crystals, a large beaker of
distilled water, a d.c. power supply and connecting wires
(8 marks)
4.
Chemical Knowledge (5 marks)
Dissolve the nickel(II) sulphate crystals in the distilled water (in the beaker)
Connect the clean metal spoon to the negative terminal and the nickel plate to the
positive terminal of the power supply/connect the spoon and the nickel plate to the
power with the spoon as the cathode and the nickel plate as the anode
Immerse/dip the spoon and the nickel plate in the nickel(II) sulphate solution.
Observation (Any TWO of the following)
a layer of nickel (silvery/greyish metal) is deposited onto the spoon
the thickness of the nickel plate decreases
the colour of the nickel(II) sulphate solution remains unchanged
Effective communication (3 marks)
General guidelines for marking effective communication:
(i) The mark for effective communication should relate to the candidate's
knowledge in chemistry. A candidates who wrote a paragraph which is
totally unrelated to the question should deserve zero mark both in chemical
knowledge and in effective communication.
(ii) The table below illustrates the relationship between the mark for chemical
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(1)
(1)
knowledge and the maximum mark for effective communication.
mark for chemical
maximum mark for
points to be considered in
knowledge
effective communication
paragraph (iii) below
4 or above
3
(A), (B) and (C)
3 or below
2
(B) and (C)
(iii) The three marks for effective communication are awarded as follows:
(A) the ability to present ideas in a precise manner, including the correct
use of chemical terms (this mark should not be awarded to answers
which contained a lot of incorrect/superfluous materials);
(B) the ability to present ideas in a systematic manner (i.e., the answer is
easy to follow);
(C) the ability to present answer in paragraph form and to express ideas
using full sentence.
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5.
In March 1989, the oil tanker Exxon Valdez was wrecked off the coast of Alaska and spilt a
large amount of crude oil into the sea. The oil spillage caused serious environmental
problems.
Briefly explain why oil spillage in the sea can cause serious environmental problems and
suggest ONE method of treating the spilt oil.
(8 marks)
5.
Chemical Knowledge (5 marks)
Environmental problems caused by oil spillage:
(Any FOUR of the following, one mark for each point)
oil is less dense than water and is insoluble in it/is immiscible with water, the
oil layer can block the oxygen supply to marine life/cause the death of
marine life
oil is flammable
oil washed ashore may spoil the beaches
the decomposition of oil is slow and the effect is long lasting
oil clogs the feathers of sea birds and prevent them from flying or
swimming/oil interferes with the insulation provided by the feathers of sea
birds, so the sea birds may die of cold or pneumonia
oil layer blocks the sunlight from penetration into sea water and hinders the
photosynthesis of aquatic plants
oil is toxic/poisonous
if detergent is used to clean up the spilt oil, the detergent remained in the sea
may cause harm to marine life
Treatment of oil spillage:
(Any ONE of the following)
treat oil with detergent which can emulsify the oil/break down oil into
droplets
use floating barrier or boom to prevent the spread of oil
use micro-organism to break down the oil
Effective communication (3 marks)
General guidelines for marking effective communication:
(i) The mark for effective communication should relate to the candidate's
knowledge in chemistry. A candidates who wrote a paragraph which is
totally unrelated to the question should deserve zero mark both in chemical
knowledge and in effective communication.
(ii) The table below illustrates the relationship between the mark for chemical
knowledge and the maximum mark for effective communication.
mark for chemical
maximum mark for
points to be considered in
knowledge
effective communication
paragraph (iii) below
4 or above
3
(A), (B) and (C)
3 or below
2
(B) and (C)
(iii) The three marks for effective communication are awarded as follows:
(A) the ability to present ideas in a precise manner, including the correct
use of chemical terms (this mark should not be awarded to answers
which contained a lot of incorrect/superfluous materials);
(B) the ability to present ideas in a systematic manner (i.e., the answer is
easy to follow);
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(C)
the ability to present answer in paragraph form and to express ideas
using full sentence.
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Section B (Answer any THREE questions.)
6.
(a)
A student used the following experimental set-up to study the migration of ions.
filter paper moistened with
microscope slide
sodium sulphate solution
crocodile clip
crocodile clip
A
B
_
C
+
d.c. supply
The student placed a drop of potassium dichromate solution at A and a drop of a deep
blue solution at C. It is known that the two solutions do not react and the deep blue
colour of the solution at C is due to the cation present.
(i) Write the formula of the ion responsible for the orange colour of potassium
dichromate.
(ii) Why was the filter paper moistened with sodium sulphate solution?
(iii) An electric current was passed through the circuit for some time.
(1) What would be the colour change at A?
(2) What would be the colour change at B? Explain your answer.
(iv) Using the same apparatus and materials, suggest how you could show that the
colour changes in (iii) are NOT due to diffusion.
(8 marks)
6.
(a)
(i)
Cr2O72
(ii) The sodium sulphate solution provides ions for the conduction of
electricity/acts as an electrolyte/complete the circuit
(iii) (1) The orange colour becomes paler/colourless/fades
(2) Green/brown/purple colour was observed
Explanation: Under the influence of the electric field, cations in
the deep blue solution are attracted to the negative pole (move
2
to the left) and negative/ Cr2O7
ions are attracted to the
positive pole (move to the right).
or, Under the influence of the electric field, the cations and
anions are respectively attracted towards the negative and
positive poles
The orange negative ions and the blue positive ions mix/meet at
B to give the green colour.
(iv) reverse the polarity of the d.c. supply
or, connect the left hand electrode to the positive pole and the right
hand electrode to the negative pole
Observation: orange colour will appear at the left of A and blue colour
will appear at the right of C
(b)
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In a certain country, sulphuric acid is manufactured by the Contact Process using
sulphur as the raw material. The uses of sulphuric acid in this country are summarized
in the following pie-chart.
Fertilizers
37%
Paints
16%
Fibres
14%
Others
23%
Soaps and
detergents
10%
(i)
The stages involved in the Contact Process can be represented by the following
equations:
S(s)  O2 (g)  SO2 (g)
2SO2 (g)  O2 (g)
2SO3 (g)

SO3 (g)  H 2SO4 (l)
H 2S 2 O 7 ( l )
H 2S2 O7 (l)  H 2 O(l)  H 2SO 4 ( l)
Suppose that the conversion of sulphur to sulphuric acid is 100%.
(1) How many moles of sulphur are required to produce one mole of
sulphuric acid?
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(2) If the annual production of sulphuric acid in this country is 2.6  10 kg,
calculate the annual consumption of sulphur, in kg, in the Contact Process.
(3) Referring to the above equations, explain why the actual annual
consumption of sulphur is greater than the value calculated in (2).
(ii) Suggest ONE other method that can be used to produce sulphur dioxide
required for the Contact Process. Write the chemical equation(s) involved.
(iii) As we enter the twentieth century, global demand for fertilizers is increasing
annually.
(1) Name ONE fertilizer which can be made from sulphuric acid.
(2) Explain why global demand for fertilizers is increasing annually.
(iv) Sulphuric acid is also used in the paint industry. Suggest ONE paint additive
that can be prepared from sulphuric acid.
(v) Suggest ONE use of sulphuric acid categorized as 'Others' in the pie chart.
(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1)
(10 marks)
6.
(b)
(i)
(1)
One/1
1
(2)
Relative molecular mass of H 2SO 4 = 2 + 32.1 + 4×16 = 98.1
32.1

 2.6  109
981
.
Annual consumption of sulphur
1
.  108 (kg)
= 851
.  108 to 851
.  108 kg)
(Accept answers from 850
The conversion of SO 2 to SO 3 is a reversible reaction
(ii)
(3)
Roasting/heating metal (iron/zinc) pyrites/sulphides
4 FeS2  11O2  2 Fe2 O3  8SO2
2 ZnS  3O2  2 ZnO  2SO2
(Accept equations showing the roasting of other metal sulphides.)
or, Heating calcium sulphate/anhydrite with coke
CaSO4  2C  CaS  2CO2
CaS  3CaSO4  4CaO  4SO2
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or, Burning hydrogen sulphide (from natural gas/oil refinery
gases/coal gas manufacture)
2 H 2S  3O2  2SO2  2 H 2 O
(iii) (1) †ammonium sulphate/ammonium super-phosphate
(2) application of fertilizer can increase agricultural yield so as to
meet the growth of population/replenish the loss of nutrient in
soil caused by excessive farming
(iv) barium sulphate/calcium sulpahte/ BaSO 4 / CaSO 4
(v)
7.
(a)
pickling of metal in electro-plating industry/production of drain
cleaner/electrolyte in lead-acid accumulators/use as laboratory
reagents/making dye stuff.
(Accept any correct use of sulphuric acid in broad terms)
(1)
(1)
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Malachite is a mineral containing copper(II) carbonate and copper(II) hydroxide. It is
insoluble in water but reacts with dilute sulphuric acid. The procedure for preparing
copper(II) sulphate crystals from malachite is as follows:
Step 1 Pour 50 cm3 of 2 M sulphuric acid in a beaker and then warm the acid.
Step 2
Add small portions of powdered malachite to the warm acid while
constantly stirring, until effervescence stops and some powdered
malachite remains in the beaker.
Step 3 Remove the remaining powdered malachite from the solution.
Step 4 Evaporate the solution slowly to obtain copper(II) sulphate crystals.
(i) Write a chemical equation for the reaction which causes the effervescence.
(ii) Why is it necessary to add powdered malachite until some of it remains in the
beaker?
(iii) Draw a labelled diagram to show how the remaining powdered malachite can
be removed from the solution.
(iv) Calculate the theoretical mass of copper(II) sulphate crystals, CuSO 4  5H 2 O ,
that can be obtained.
(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, S = 32.1, Cu = 63.5)
(8 marks)
7.
(a)
(i)
CuCO3  Cu(OH ) 2  2 H 2SO4  2CuSO4  3H 2 O  CO2

2
or, CuCO3  Cu(OH)2  4H  2Cu  CO2  3H2O
or, CuCO3  H 2SO4  CuSO4  H 2 O  CO2
(ii)

2
or, CuCO3  2H  Cu  CO2  3H2O
To ensure that all the sulphuric acid has been used up/malachite is in
excess
1
(1)
(1)
(1)
1
(iii)
3
(Award 0 mark for this part if the set-up is not workable.)
(1 mark for showing the filter funnel and filter paper; 1 mark for
showing the collection of the filtrate; 1 mark for labelling filter paper
and residue)
(iv) No. of moles of H 2SO 4 used  2  50  103
= 0.1
CuSO

5
H
4
2 O produced = 0.1
No. of moles of
Formula mass of CuSO 4  5H 2 O
= 63.5 + 32.1 + 4×16.0 + 5×(2×1.0+16.0)
= 249.6
Theoretical mass of CuSO 4  5H 2 O
= 0.1×249.6
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1
= 24.96 g
(Also accept 25.0 g and 25 g; deduct 1 mark for wrong/no unit.)
(b)
The structures of five compounds, I, II, III, IV and V, are shown below:
In the above structures,
represents a saturated hydrocarbon chain containing 1
to 6 carbon atoms and
represents a saturated hydrocarbon chain containing
12 to 20 carbon atoms.
(i) Which compound can be used to make an addition polymer? Write a chemical
equation to represent the addition polymerization.
(ii) Which TWO compounds can be used to make a condensation polymer? Draw
the repeating unit of the polymer formed.
(iii) Upon heating with sodium hydroxide solution, one of these compounds
produces a soapy detergent.
(1) What is this compound?
(2) Draw the structure of the soapy detergent produced.
(3) Briefly explain the emulsifying action of the detergent when it is used to
remove greasy dirt.
(10 marks)
7.
(b)
(i)
1
IV/
1
(ii)
II and III
(iii) (1)
(2)
I
1
1
1
1
(3)
The hydrocarbon end/tail is hydrophobic/readily soluble in the
greasy dirt

The COO (ionic) end is hydrophilic/readily soluble in water
Agitation/stirring will cause the grease to break down into
droplets.
The negative charge on the droplets repels each other and hence
oily droplets will become suspended in the aqueous solution.
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8.
(a)
A class of students visited a chemical plant which manufactures chlorine by the
electrolysis of brine. Some of the chlorine produced is used to make chlorine bleach.
At the end of the visit, each student was given a bottle of chlorine bleach as a gift.
(i) Explain, in terms of preferential discharge of ions, how chlorine is produced in
the electrochemical process.
(ii) The students found some metal cylinders containing chlorine in the chemical
plant. The students were told that these cylinders would be used in water
treatment plants.
(1) Which one of the following hazard warning labels should be displayed on
the metal cylinder?
A
B
C
D
(2) Explain why chlorine is used in water treatment plants.
(iii) Suggest ONE product, apart from chlorine and chlorine bleach, likely to be
manufactured in the chemical plant.
(iv) When the students returned to the school, their teacher asked them to carry out
an experiment using the chlorine bleach as illustrated below.
(1)
(2)
8.
(a)
(i)
Write the ionic equation for the reaction of dilute hydrochloric acid with
the chlorine bleach.
State the observable change that would occur on the filter paper. Explain
whether or not the change would involve a redox reaction.
(9 marks)


During electrolysis, both Cl and OH ions migrate towards the

anode/+ve electrode. Since the concentration of Cl ions is (much)

higher than that of OH /a concentrated NaCl (brine) is used
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Cl  ions will be discharged (in preference of OH  ) at the anode to
give chlorine


or, 2Cl  Cl2  2e
(ii)
(1) B/toxic
(2) chlorine can kill the bacteria/germs in water/sterlize water
(iii) sodium hydroxide/hydrochloric acid/hydrogen



(iv)
(1) 2H  OCl  Cl  H 2O  Cl2
(2)
8.
a brown colour is observed
A redox reaction has occurred because the oxidation no. of Cl
changes (from 0 to -1)
or, the oxidation no. of I changes (from -1 to 0)
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(b)
Read the following paragraph concerning chromium and answer the questions that
follow:
The Greek word "chrõma" means colour. Many chromium-containing
compounds and chromium containing gemstones are beautifully coloured.
The oxidation number of chromium in its compounds can be +2, +3 and
+6.
(i) Jade, a green-coloured gemstone, is chromium-containing. Suggest what
chromium ion present in jade is responsible for its green colour.
(ii) Potassium dichromate is an oxidizing agent. The oxidation number of
chromium in potassium dichromate is +6.
(1) Name ONE compound which can be oxidized by potassium dichromate.
(2) State the condition(s) under which the compound reacts with potassium
dichromate.
(3) What product is formed from the compound in the redox reaction?
(iii) In the presence of a dilute acid, chromium(II) ions react with atmospheric
oxygen to form chromium(III) ions and water.
(1) Write the half equation for the formation of chromium(III) ions.
(2) Write the half equation for the formation of water.
(3) Write the overall equation for the reaction.
(iv) Suggest TWO ways in which chromium can be used to prevent the corrosion of
iron.
(9 marks)
(b)
(i)
(ii)
3
chromium(III)/ Cr
(1) †Iron(II)
sulphate
(any
iron(II)
compound)/sulphur
dioxide/ethanol/potassium iodide/hydrogen sulphide
(Accept name of reducing agent (compound ONLY) which can
reduce potassium dichromate).
(2) For iron(II) sulphate (the iron(II) compound in (1))
Treat
CaSO4
1
with acidified potassium dichromate/in the

presence of acid/ H ions
For SO 2
1
Bubble SO 2 into acidified postassium dichromate
(or place a piece of filter paper moistened with acidified
potassium dichromate in SO 2 gas)
(1)
For ethanol
heat/reflux ethanol with acidified potassium dichromate
For KI
Treat KI(aq) with acidified potassium dichromate
For H 2S
Bubble H 2S(g) into acidified potassium dichromate
(or place a piece of filter paper moistened with acidified
potassium dichromate in H 2S gas)
(3)
1
3
For Fe(II): Fe /iron(III) ions
(1)
(1)
(1)
1
For KI: I 2 /iodine
For H 2S : S/sulphur
(1)
(1)
1
O2  4e  4H   2H2O
1

2
3
(3) O2  4H  4Cr  4Cr  2H2O
(iv) making stainless steel
chromium-plating
1
(1)
(2)
(a)
(1)
Cr 2   Cr 3  e 
(iii)
9.
2
For SO 2 : SO4 (aq) /sulphate ions
For C2 H 5OH : CH 3COOH /ethanoic acid/ CH 3CHO /ethanal
1
1
The photograph below shows a gas burner with a can of fuel. The can contains 250 g
of liquified butane.
(i)
(ii)
Write the structure formula of butane.
(1) Write the chemical equation for the complete combustion of butane.
(2) Suggest a chemical test for EACH of the products formed when butane is
completely burnt in air.
(3) Calculate the volume of the gaseous product formed, measured at room
temperature and pressure, if all the butane contained in the can is
completely burnt in air.
(iii) Explain why it is dangerous to use such gas burners in a poorly-ventilated room.
(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0;
3
molar volume of gas at room temperature and pressure = 24.0 dm )
(9 marks)
9.
(a)
(i)
CH 3CH 2 CH 2 CH 3 /
(ii)
(1)
2C4 H10  13O2  8CO2  10H 2 O
13
O 2  4CO2  5H 2 O
2
or,
carbon dioxide can turn lime water milky
water cna turn anhydrous copper(II) sulphate from white to
blue/anhydrous cobalt(II) chloride (paper) from blue to pink
relative molecular mass of butane = 12×4 + 1×10 = 58
250

 4.31
58
no. of moles of butane in the can
Upon complete combustion, 1 mole of butane produces 4 moles
of carbon dioxide
250
 4
 24.0 dm3
58
Volume of gas produced
C 4 H10 
(2)
(3)
3
= 414 dm
3
(Accept answers from 412 to 414 dm ; deduct 1 mark for
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1
1
1
wrong/no unit)
(iii) Incomplete combustion of butane may occur which produces carbon
monoxide/CO which is toxic/poisonous
(b)
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X and Y are different metals. A student studied the reactivity of X, Y and copper by
setting up two electrochemical cells using the following materials and apparatus:
The results of the experiment are tabulated below:
Electrochemical cell
Direction of electron flow in
the external circuit
formed by connecting half-cells A and C
Y to Cu
formed by connecting half-cells B and C
X to Y
(i) What is the meaning of the term 'saturated solution'?
(ii) Explain the use of the strips of filter paper in the experiment.
(iii) The student had to use an additional instrument to determine the direction of
electron flow in the external circuit.
(1) What instrument did the student use?
(2) Draw a labelled diagram to show the set-up for the experiment, using
half-cells A and C.
(iv) Arrange X, Y and copper in the order of increasing reactivity. Explain your
answer.
(v) What would be observed when a piece of copper foil is immersed in an aqueous
3
2
solution containing 1 moldm
of Y
ions? Explain your answer.
(9 marks)
9.
(b)
A solution containing the maximum amount of a solute ( KNO 3 ) at a
specified temperature.
(Accept any correct definition of saturated solution.)
(ii)
KNO3
The strips of filter paper, after soaked with the saturated
solution, is used as a bridge (to complete the circuit)
(iii) (1) voltmeter/ammeter/multimeter/galvanometer
(2)
(i)
1
1
1
2
(Award 0 mark for this part if the set-up is not workable.)
(1 mark for a correct diagram; 1 mark for labelling the half-cells
and the voltmeter/ammeter/multimeter/galvanometer)
(iv) Reactivity: Cu < Y < X
A more reactive metal loses electrons more readily than 1 less
1
(v)
reactive metal
or, electrons flow from a more reactive metal to a less reactive metal.
or, electrons flow from X to Y and from Y to Cu
no observable change
because Cu is less reactive than Y
END OF PAPER
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