S.4 Chemistry Supplementary Exercise 2014-2015
Name: _________________________________
Class and class number: S.4 ___ (
Block: _____
)
Part A: Multiple choice questions
1.
Oxygen can be obtained from the
(1) fractional distillation of liquefied air.
(2) reaction between calcium and water.
(3) electrolysis of dilute sodium chloride solution with graphite electrodes.
A.
2.
3.
4.
B.
(2) only
C.
(1) and (3) only
D.
(2) and (3) only
Lithium has two isotopes, 6Li and 7Li. The relative abundance of 7Li is 92.5%. Which of the following
statements about the two isotopes is INCORRECT?
A.
7
B.
They have the same number of outermost shell electrons.
C.
The relative atomic mass of lithium is 6.93.
D.
They give out flames of different colours in the flame test.
Li has one more neutron than 6Li.
Which of the following statements about bromine and chlorine is correct?
A.
Both of them are coloured gases at room temperature and pressure.
B.
Bromine is more reactive than chlorine.
C.
Both of them are poisonous.
D.
Both of them react with sodium to form simple molecular substances.
Metal X forms a phosphate with the formula X3(PO3)2. What is the chemical formula of its
hydrogencarbonate?
A.
5.
(1) only
XHCO3
B.
X(HCO3)2
C.
X3(HCO3)2
D.
X(HCO3)3
Which of the following combinations about the atomic structure of 26Mg2+ is correct?
Number of protons
Number of neutrons
Number of electrons
A.
13
12
11
B.
13
12
15
C.
12
13
10
D.
12
14
10
6.
In which of the following tubes will the iron nail rust after a few days?
(1)
A.
7.
8.
(2)
(3)
iron nail
air
iron nail
air
iron nail
0.1 M sodium
hydroxide
solution
0.1 M calcium
chloride solution
0.1 M sodium
hydroxide
solution
(1) and (2) only
B.
(1) and (3) only
C.
(2) and (3) only
D.
(1), (2) and (3)
Which of the following samples contains the largest number of atoms?
A.
5.0 g of carbon dioxide
B.
5.0 g of steam
C.
5.0 g of nitrogen
D.
5.0 g of sulphur trioxide
Which of the following hazard warning labels should be displayed on a bottle of concentrated sulphuric
acid?
A.
and
B.
and
C.
and
D.
and
9.
A mixture of copper(II) sulphate and copper(II) bromide contains 0.3 mole of sulphate ions and 0.6 mole
of bromide ions. How many moles of copper(II) ions are in the mixture?
A. 0.6 mol
B. 0.8 mol
C. 0.9 mol
D. 1.1 mol
10. In the Ostwald Process, the following reaction occurs:
4NH3(g) + 5O2(g)  4NO(g) + 6H2O(l)
Which of the following statements about ammonia is/are correct?
(1)
It is the reducing agent.
(2)
The oxidation number of nitrogen in ammonia decreases.
(3)
It loses electron(s).
A.
(1) only
B.
(2) only
C.
(1) and (3) only
D.
(2) and (3) only
11. The following diagram shows a simple chemical cell.
salt bridge
graphite electrode
graphite electrode
silver sulphite solution
acidified potassium
permanganate solution
Which of the following statements concerning the above chemical cell are INCORRECT?
(1) Electrons flow from the right electrode to the left electrode in the external circuit.
(2) Potassium chloride solution can be used as an electrolyte in the salt bridge.
(3) The colour of acidified potassium permanganate solution changes from purple to colourless.
A.
(1) and (2) only
B.
(1) and (3) only
C.
(2) and (3) only
D.
(1), (2) and (3)
12. Which of the following statements concerning the electrolysis of copper(II) sulphate solution using
graphite electrodes are correct?
(1)
The pH value of the solution gradually decreases.
(2)
Copper is deposited at the cathode.
(3)
Hydrogen gas is given off at the anode.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
13. Which of the following compounds when heated can produce a gas that relights a glowing splint?
A. Copper(II) oxide
B. Silver oxide
C. Calcium oxide
D. Iron(III) oxide
14. An element forms a compound X2Cl3 which contains 25% by mass of chlorine. What is the relative atomic
mass of the element X?
(Relative atomic mass: Cl = 35.5)
A.
39.9
B.
79.9
C.
106.5
D.
159.8
15. Which of the following statements concerning the electrolysis of concentrated sodium bromide solution
using graphite electrodes are correct?
(1) The main product at the anode is O2(g).
(2) H+(aq) ions are preferentially discharged at the cathode to form H2(g).
(3) The solution becomes sodium hydroxide solution after electrolysis.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
16. Which of the following is the correct order of melting point of Na2O, SiO2 and SO2?
A. Na2O < SiO2 < SO2
B. SO2 < Na2O < SiO2
C. SiO2 < Na2O < SO2
D. SO2 < SiO2 < Na2O
17. 5.20 g of a dibasic acid H2X dissolves completely in distilled water and is then diluted to 250.0 cm3. 25.0
cm3 of the diluted solution requires 20.0 cm3 of 0.50 M sodium hydroxide solution for complete
neutralization. What is the molar mass of the acid?
A. 52.0 g mol1
B. 104.0 g mol1
C. 260.0 g mol1
D. 520.0 g mol1
18. Consider the following chemical equation:
2MnO4(aq) + xH2O2(aq) + yH+(aq)  2Mn2+(aq) + xO2(g) + zH2O(l)
Which of the following combinations is correct?
x
y
z
A.
1
8
4
B.
1
8
8
C.
5
10
4
D.
5
6
8
19. In which of the following atoms or ions is the outermost shell an octet?
(1) Li+
(2) Ar
(3) P3–
A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
20.
X, Y and Z are metals. The table below shows the observations when each of them is put into copper(II)
sulphate solution:
Metal
Observation
X
no observable change
Y
brown solid formed and colourless gas evolved
Z
brown solid formed
Which of the following arrangements correctly represents the ascending order of reactivity of the metals?
A. X < Z < Y
B. Y < Z < X
C. Z < X < Y
D. X < Y < Z
21. The oxide of metal Z reacts with dilute hydrochloric acid to form a colourless solution. Which of the
following metals may Z be?
(1) zinc
(2) copper
A. (1) only
(3) silver
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
22. Which of the following pairs of ions would react together to form a white precipitate?
A. Ca2+(aq) and SO42– (aq)
B. Ni2+(aq) and NO3– (aq)
C. Cu2+(aq) and OH–(aq)
D. NH4+(aq) and OH–(aq)
23. Oxalic acid is a dibasic acid. 10.0 cm3 of an aqueous solution of oxalic acid requires 30.0 cm3 of 0.1 0 M
KOH(aq) for complete neutralisation. What is the concentration of the oxalic acid solution?
A. 0.15 M
B. 0.20 M
C. 0.30 M
D. 0.60 M
24. X is an acid. 25.0 cm3 of 0.20 M solution X requires 30.0 cm3 of 0.50 M sodium hydroxide solution for
complete neutralisation. What is the basicity of X?
A. 1
B. 2
C. 3
D. 4
25. Which of the following substances can decolourise acidified potassium permanganate solution?
(1) sodium nitrate solution
A. (1) only
(2) sodium sulphite solution
B. (2) only
(3) chlorine water
C. (1) and (3) only
D. (2) and (3) only
26. The following diagram shows the set-up of a chemical cell.
Given that Br2(aq) is a stronger oxidising agent than Fe3+(aq), which of the changes represented by the
following half equations would occur if the cell is producing a current?
(1) Fe3+(aq) + e– → Fe2+(aq)
(2) Fe2+(aq) → Fe3+(aq) + e–
(3) 2 Br–(aq) → Br2(aq) + 2 e–
A. (1) only
27.
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
In an experiment of electroplating nickel on a copper object, which of the following combinations is
correct?
Anode
Cathode
Electrolyte
A. copper object
nickel
CuSO4(aq)
B. copper object
nickel
NiSO4(aq)
C. nickel
copper object
CuSO4(aq)
D. nickel
copper object
NiSO4(aq)
28. A sample of zinc granules of mass 1.8 g was added to 100 cm3 of 0.25 M hydrochloric acid. What is the
theoretical volume of hydrogen produced at room temperature and pressure?
(Relative atomic mass: Zn = 65.4; molar volume of gas at room temperature and pressure = 24 dm3)
A. 0.025 g
B. 0.028 dm3
C. 0.050 g
D. 0.055 g
29. Methane (CH4) burns completely in oxygen according to the following equation:
CH4 + 2O2 → CO2 + 2H2O
What is the mass of oxygen required for the complete combustion of 48 g of methane?
(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)
A. 48 g
B. 96 g
C. 192 g
D. 384 g
30. In which of the following compounds does sulphur exhibit the lowest oxidation number?
A. Na2S2O3
B. MgSO4
C. KHSO3
D. H2S2O7
31. Which of the following statements concerning the reaction between carbon and concentrated sulphuric acid
are correct?
(1) The oxidation number of carbon changes from 0 to +4.
(2) The oxidation number of hydrogen in sulphuric acid remains unchanged.
(3) Concentrated sulphuric acid acts both as a dehydrating agent and an oxidising agent.
A. (1) and (2) only
Directions:
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
Each question below (Questions 32 to 33) consists of two separate statements. Decide whether
each of the two statements is true or false; if both are true, then decide whether or not the second
statement is a correct explanation of the first statement. Then select one option from A to D
according to the following table:
A. Both statements are true and the 2nd statement is a correct explanation of the 1st
statement.
B. Both statements are true and the 2nd statement is NOT a correct explanation of the 1st
statement.
C. The 1st statement is false but the 2nd statement is true.
D. Both statements are false.
1st statement
2nd statement
32. Graphite is a good conductor of
electricity.
In graphite, layers of carbon atoms are
held together by weak van der Waals’
forces.
33. Ethanoic acid is a weak acid.
Ethanoic acid ionizes slightly in water to
form hydrogen ions.
Part B: Structured questions
1. In a copper electroplating factory, waste water is treated to remove the copper (II) ions before being
discharged. Describe how the process can be done. Write an ionic equation involved in the process.
[3 marks]
2. The active ingredients of a fizzy drink powder are citric acid, sodium carbonate and sodium hydrogen
carbonate. When water is added onto the powder, some colourless gas bubbles are formed. The colourless
gas is collected as shown in the following apparatus:
(a) (i) What is the colourless gas collected
in the gas jar?
Water
[1 mark]
Colourless gas
Fizz drink
powder
(ii) Write an ionic equation to show the formation of the gas as a result of the
active ingredients in the presence of water.
[1 mark]
(b) Suggest a suitable way to store fizzy drink powder or tables. [1 mark]
reaction between
(c) Citric acid is a weak acid. Its structure is shown on the right:
(i) Explain why citric acid is a weak acid.
[1 mark]
CH2COOH
HO
C
COOH
CH2COOH
(ii) What is the basicity of citric acid?
[1 mark]
(d) If an organic solvent, methylbenzene, is added into the fizz drink instead of water, no gas is collected.
Explain the phenomenon.
[1 mark]
3. A soluble salt, ammonium sulphate, (NH4)2SO4, is a fertilizer that can be prepared in the laboratory by
titration in which sulphuric acid is neutralized by ammonia solution.
(a) Write an equation to show that ammonia solution is a weak acid.
[1 mark]
(b) Apart from preparing salt, suggest a domestic use of ammonia solution.
[1 mark]
(c) 50 cm3 of 1M sulphuric acid is added to ammonia solution.
(I) Write a chemical equation for the reaction between ammonium sulphate and sulphuric acid. [1 mark]
(II) Calculate the mass of ammonium sulphate obtained when all the sulphuric acid has been reacted.
(Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, S = 32.1)
[2 marks]
4. A domestic drain cleaner contains concentrated sodium hydroxide solution as the active ingredient. We can
use titration to determine the concentration of sodium hydroxide solution in the drain cleaner by the
following procedures.
(I) 25.0 cm3 of the drain cleaner was diluted to 250.0 cm3 with distilled water.
(II) 25.0 cm3 of the diluted solution were then titrated against 0.5 M sulphuric acid solution. 26.8 cm3 of
0.5 M sulphuric acid were required for complete neutralization.
Refer to procedure I.
(a) Describe how concentrated sodium hydroxide solution in the drain cleaner should be diluted. You must
specify the volume and apparatus used.
[3 marks]
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
(b) State TWO safety precautions that should be taken when handling concentrated sodium hydroxide
solution.
[2 marks]
________________________________________________________________________________
(c) Which of the following hazard warning labels should be displayed on the container containing
concentrated sodium hydroxide solution? State the meaning of the selected label.
[1 mark]
A
B
C
D
__________________________________________________________________________________
Refer to procedure II.
(d) Write the equation of neutralization between sodium hydroxide and sulphuric acid.
[1 mark]
(e) Calculate the number of moles of sodium hydroxide in 25.0 cm3 of the diluted solution.
[2 marks]
(f) Calculate the molarity (M) of diluted sodium hydroxide solution.
[1 mark]
(g) Calculate the molarity of concentrated sodium hydroxide solution in the drain cleaner.
[2 marks]
(Relative atomic masses: H = 1.0, O = 16.0, Na = 23.0)
5.
Describe how you could make a dry sample of magnesium chloride crystals from magnesium carbonate
and dilute hydrochloric acid.
(9 marks)
6.
In a titration analysis, a standard hydrochloric acid was used to determine the percentage purity of a sample
of calcium oxide.
(a) What is meant by the term ‘standard solution’?
(1 mark)
(b) A student prepared the standard hydrochloric acid by diluting a concentrated hydrochloric acid of
known concentration.
(i)
Describe briefly the procedure for the dilution.
(ii) It was found that the concentration of the solution prepared in (i) is less than expected. Explain
briefly.
(iii) Suggest a method to determine the concentration of hydrochloric acid prepared in (i).
(5 marks)
6.
(c)
The concentration of the standard hydrochloric acid was determined to be 1.23 M. 1.78 g of
an impure sample of calcium oxide required 28.40 cm3 of 1.23 M hydrochloric acid for complete
neutralization. Calculate the percentage purity of calcium oxide sample.
(Assume that the impurities in the sample do not react with hydrochloric acid.)
(3 marks)
7. The wastewater generated from all electroplating factory contains dichromate ions. Before the wastewater is
discharged, it is treated in two stages as described below to remove the chromium-containing substances.
Stage 1: Treat the wastewater with excess sodium sulphite solution in the presence of acid to reduce
the dichromate ions to chromium(III) ions.
Stage 2:
Add a suitable chemical to the treated wastewater from to precipitate the chromium(III) ions.
(a) Why is it necessary to remove chromium-containing substances from the wastewater?
[1 mark]
(b) In Stage 1, the sulphite ions are oxidised to sulphate ions by the dichromate ions.
(i) Write the half equation for the oxidation of sulphite ions.
(ii) Write the half equation for the reduction of dichromate ions
(iii)Write the overall equation for the redox reaction.
[3 marks]
(c) Suggest a suitable chemical for the precipitation of chromium(III) ions in Stage 2.
[1 mark]
8. For each of the following experiments, state an expected observation and write a chemical equation for the
reaction involved.
[6 marks]
(a) A magnesium ribbon is placed in a Bunsen flame.
(b) Excess iron(II) sulphate solution is added to an acidified potassium permanganate solution.
(c) Chlorine gas is bubbled into a sodium bromide solution.
9. Discuss the similarities and differences in chemical properties of concentrated sulphuric acid and dilute
sulphuric acid. Illustrate your answer using appropriate examples.
[9 marks]
10. The diagram below shows the set-up used in performing a microscale experiment. A drop of hydrochloric
acid was added to the drop of chlorine bleach in a petri dish and the dish was immediately covered with its
lid. Chlorine gas formed by the reaction between chlorine bleach and hydrochloric acid eventually filled up
the whole set-up.
(a) State the expected observation at position C and position D. In each case, write a relevant ionic
equation if a reaction occurred.
[3 marks]
(b) Suggest one advantage of replacing test tube experiments with microscale experiments.
11.
[1 mark]
The following two methods can be used to convert copper metal to copper (II) nitrate solution.
dilute HNO3 (aq)
Method 1:
Cu (s)
CuO (s)
Cu(NO3)2 (aq)
dilute HNO3 (aq)
Method 2:
(a)
Cu (s)
Cu(NO3)2 (aq)
Refer to Method 1,
(i)
Suggest how copper metal can be converted to copper (II) oxide. State the expected
observation in the reaction that you have suggested. (2 marks)
(ii)
Name the type of reaction that occurs between copper (II) oxide and dilute nitric acid.
(1 mark)
*12.
(b)
Write a chemical equation, with state symbols, for the reaction involved in Method 2. (2 mark)
(c)
Which of these methods would you recommend for the conversion of copper metal into copper
nitrate solution? Justify your answer with ONE reason.
(1 mark)
You are given four unlabeled bottles, each containing one of the following solutions. Describe and give
the results of the tests that you would carry out to identify the content of each bottle.
ZnSO4(aq), (NH4)2SO4(aq),
MgCl2(aq), K2SO4(aq)
(5 marks)
13.
Consider the set-up below.
When the circuit is closed, current flows in the external circuit. A reddish brown deposit is found on the
electrode made of metal M after some time.
(a)
What is the direction of electron flow in the external circuit? Explain your answer.[1 mark]
(b)
What is the function of set-up X in this experiment?
[1 mark]
(c)
Suggest what metal M may be.
[1 mark]
(d)
What would be observed at the copper electrode?
[1 mark]
(e)
Describe and explain what would happen
(i)
at carbon electrode A,
(ii) and carbon electrode B.
[2 marks]
[2 marks]
14. In an acidic medium, hydrogen peroxide (H2O2) oxidizes thiosulphate ions (S2O32-) to sulphate ions and
itself is reduced to water.
(a) What is the oxidation number of the underlined element in each of the following substances?
(1) H2O2
(2)
S2O32[1 mark]
(b) Write an IONIC equation for the reaction between hydrogen peroxide and thiosulphate ions. [1 mark]
(c) (1) Bromine stains on laboratory coats can be removed chemically by treating with sodium
thiosulphate solution. Explain the principle behind.
[2 marks]
(2) Aqueous bromine and aqueous iodine of low concentration are both yellow in color. Suggest a
method to identify a solution containing bromine but not iodine.
[2 marks]
15.
Coal-burning power stations produce sulphur dioxide and oxides of nitrogen.
(a)
Describe how sulphur dioxide and oxides of nitrogen are formed in the power stations.[2 marks]
Sulphur-containing fuel burns to give sulphur dioxide during combustion [1]
The atmospheric nitrogen reacts with oxygen [0.5] under high heat [0.5] to produce nitrogen
monoxide, which is further oxidized to form nitrogen dioxide
(b) Many coal-burning power stations are now fitted with a flue gas desulphurisation plant which
removes sulphur dioxide from the gaseous emissions.
In a flue gas desulphurisation plant, powdered calcium carbonate reacts with sulphur dioxide as
shown.
SO2(g) + CaCO3
(i)
3(s)
+ CO2(g)
Suggest why the calcium carbonate is powdered.
[1 mark]
To increase the surface area for faster reaction [1]
(ii) Calculate the mass of calcium carbonate needed to react with 8000 kg of sulphur dioxide.
[2 marks]
no. of moles of sulphur dioxide = 8000 000 / (32.1 + 16 x 2 ) = 124805
mass of calcium carbonate
= 124805 [40.1 +12 + 16 x 3]
[0.5]
[0.5]
= 12492980 g
[1]
(c) Explain how sulphur dioxide may affect the environment.
[2 marks]
Sulphur dioxide dissolves in rain water to from sulphurous acid [0.5], causing acid rain [0.5].
Effects: [any 1, 1 mark]




Acid rain makes soil acidic and harmful to plants.
Acid rain makes water in rivers and lakes acidic, aquatic lives cannot survive in such acidic
environment.
Acid rain reacts with building materials, including limestone, marble, cement, which contains
mainly calcium carbonate.
Acid rain attack metal and speeds up rate of corrosion.