, Ne
B. Na, Mg2+
C. S2-, Cl D.
K+, CaPOK OI HOSPITAL TANG PUI KING MEMORIAL COLLEGE
S4
CHEMISTRY
Class : ________________ Date : __________________
Name : ________________ Time allowed: 60 minutes
Class Number : ________________ ( P.1 - P.6 /53 )
Instructions to students:
1. Answer ALL questions.
2. Write your answers on the foolscap papers provided.
3. The total score is 100 marks.
________________________________________________________________________
Section A
:Multiple Choice Questions ( 40 % )
1.
Which
of the following pairs of particles have the same electronic arrangement?
A.
F
, Ne
B. Na, Mg2+
C. S2-, Cl D.
K+, Ca
2. Which
of the following halogens is the
most reactive?
A.
Fluorine
B. Chlorine
C. Bromine
D. Iodine
¡@
3. Elements
X and Y react to form an ionic compound with a chemical formula XY2.
If X belongs to group II of the Periodic Table, to which group does Y
belong?
A.
IV
B. V
C. VI
D. VII
4.
X, Y and Z are metals. At high temperature, carbon will remove oxygen
from the oxides of Z and Y but not from that of X. Z displaces Y from a solution
of the nitrate of Y. In which of the following are the metals arranged in the
correct order of decreasing reactivity?
A. X, Y, Z
B. X, Z, Y
C. Y, Z, X
D. Z, Y, X
5. Which of the following conversions involves the smallest change in
oxidation number of the underlined element?
A. C (s) ®
CO2 (g)
B.
NO3
(aq) ®
NO2(g)
C.
SO3
(aq) ®
SO4
(aq)
D.
MnO4
(aq) ®
Mn2+ (aq)
6.
Which of the following concerning the above set-up is CORRECT?
A.
Electrons flow through the salt bridge.
B. The mass of the lead electrode remains unchanged.
C.
Oxidation occurs at the magnesium
electrode.
D. Electrons flow from the lead
electrode to the magnesium electrode through the external circuit.
7.
In the above experiment, which of the following major products will be liberated at the electrodes?
cathode
anode
8.
Which of the following aqueous solutions, when electrolysed using carbon
electrodes, will liberate only gaseous products at electrodes?
(1) KOH
(aq)
(2) AgNO3
(aq)
(3) MgCl2
(aq)
A.(1)
and (2) only
B.
(1) and (3) only
C.
(2) and (3) only
D.
(1), (2) and (3)
9.
A
student tries to electroplate an iron ring with nickel using the set-up shown
below.
Which of the following combinations is CORRECT?
Solution X
Anode
Cathode
B.
Iron(II)
sulphate solution
Nickel rod
Iron ring
C.
Nickel(II) sulphate solution
Iron ring Nickel
rod
D.
Nickel(II) sulphate solution Nickel
rod Iron
ring
10. The
cost of dry cells in decreasing order is
(1) The
alkaline manganese cell
(2) The
nickel-cadmium cell
(3) The
silver oxide cell
(4) The
zinc-carbon cell
C. (2), (3), (1), (4) D. (4), (3), (2), (1)
Section B : Questions ( 60 % )
1. Complete and
balance the following equations. Write down any observable change
you expect in each reaction.
(a)
Cl2 (aq) + Br
(aq)
(b) Fe2+
(aq) + Ag+ (aq)
(c)
SO3
(aq) + Cr2O7
(aq) + H+ (aq)
(10 marks)
2. The
following diagram shows a simple cell make by inserting a zinc strip and a
copper strip into a lemon.
(a)
Name the instrument X which is used to show the cell can generate
electricity.
(b)
Lemon juice contains citric acid which is an electrolyte. What is meant
by an electrolyte?
(c)
In which direction will electrons flow in the conducting wires?
(d)
Which is the negative terminal?
(e)
Assume the lemon juice contains H+ (aq) ions, write a half
equation for the reaction at (1) Zinc electrode, and (2) Copper electrode.
(f)
Give an ionic equation for the overall reaction of the lemon cell.
(g)
Describe the effect of the juiciness of the lemon on the voltage of the
lemon cell.
(h)
Suggest one example of low current users which can be connected to the
lemon cell.
(10 marks)
3.
When the
circuit in the set-up shown above is closed, the acidified potassium
permanganate solution loses its colour gradually.
(a) Write a half equation for the reaction that occurs in the acidified potassium permanganate solution. Explain whether the permanganate ion is oxidized or reduced.
(b) What would be observed in the potassium iodide solution after some time?
Write a half equation for the reaction that would occur. Explain whether the iodide ion is oxidized or reduced.
(c) What is the direction of electron flow in the external circuit?
(d) Write an ionic equation for the reaction that occurs when an acidified potassium permanganate solution and a potassium iodide solution are mixed together.
(e) What is function of the salt bridge in the set-up?
(10 marks)
4. The table below includes data about two types of AA-size dry cells.
|
|
Price of one packet |
Number of cells in one packet |
Life-time of cell in a torch |
|
Zinc-carbon cell |
$9.0 |
4 |
3 hours |
|
Alkaline-manganese cell |
$12.0 |
2 |
7 hours |
(a) Which type of cell is more economical for use in the torch? Explain.
(b) The following diagram shows the longitudinal section of a dry cell:
(1) Name the material commonly used for making
(i) P, and (ii) Q.
(2) Which part is the negative electrode? Write the half equation for the reaction at this electrode.
(3) Write the half equation for the reaction at the positive electrode.
(4) State the oxidizing agent.
What is the use of this oxidizing agent in the cell?
(5) A dry cell often leaks after prolonged usage. Explain the cause of leakage based on the reaction that occurs at Q.
(10 marks)
5. Briefly
describe how you would conduct an experiment, using the materials and apparatus
listed below, to copper-plate a clean metal spoon. (Diagrams are NOT required.)
State the expected observation of the experiment.
a clean metal spoon, a copper plate, copper(II)sulphate crystals, a large beaker of distilled water, a d.c. power
supply and connecting wires.
(8 marks)
(You are required to give paragraph-length
answer to this question. 3 out of the marks will be awarded for the effective
communication of knowledge in Chemisty.)
6.
The
above diagram shows a circuit for the electrolysis of dilute copper(II) sulphate
solution and dilute sodium hydroxide solution. A and B are copper electrodes
while C and D are platinum electrodes. A steady electric current is passed
through the circuit for some time.
(a)
Name the instruments represented by the symbols
and
.
What
are their functions?
(b)
Would you expect any colour change in the copper(II) sulphate solution
during electrolysis? Explain your answer.
(c)
Give half equations for the reactions that occur at electrodes C and D.
(d)
What gases are collected in the tubes above electrodes C and D
respectively.
(e)
Suggest a test for the gas collected above electrode C
(f)
What would happen to the concentration of the sodium hydroxide solution
in cell Y?
(12 marks)
END OF PAPER