HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION
CHEMISTRY PAPER 1
(Mock Examination – Marking Scheme version 2.1)
SECTION A (MULTIPLE-CHOICE QUESTIONS)
Part I
Question No.
Key
Question No.
Key
1
C
19
D
2
D
20
B
3
C
21
A
4
B
22
B
5
B
23
B
6
B
24
C
7
C
25
D
8
C
26
B
9
C
27
A
10
D
28
C
11
C
29
D
12
A
30
B
13
A
31
B
14
D
32
B
15
C
33
B
16
B
34
D
17
B
35
C
18
C
36
A
Part II
HKDSE Mock Exam
Marking Scheme
SECTION B
PART I
Marks
1
(a)
1
(no label, no mark)
(b)
Chlorine < Sodium < Magnesium
Chlorine has the lowest boiling point because it is simple molecular structure/
weak Van der Waals’ force hold the molecule.
Magnesium has the highest boing point because two electrons contribute to the
metallic bond while sodium is only one.
1
1
(c)
Element
Method of extraction
Sodium
Electrolysis of the molten ore (NaCl, rock salt)
Magnesium
Electrolysis of the molten ore (MgCO3, magnesite)
Chlorine
Electrolysis of brine/ sea water
3
2
(a)
White precipitate is formed and then redissolved.
Al3+(aq) + 3 OH-(aq)  Al(OH)3(s)
Al(OH)3(s) + OH-(aq) + H2O(l)  [Al(OH)4]- (aq)
1
1
1
(state must be written because solid is formed)
(b)
The bromine solution change from orange to colourless.
CH2CH2(g) + Br2(aq)  CH2BrCH2Br(aq)
DSE-CHEM-2
1
1
2
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HKDSE Mock Exam
Marking Scheme
Marks
3
(a)
Zinc is toxic. / Tin is non-toxic
(b)
(i)
1
number mole of Zn formed
Mass of zinc oxide
Mass of tin oxide
Mass / g
= 9.81 / 65.4
= 0.15 mol
= 0.15 x (65.5 + 16) = 12.21 g
= 49.89 - 12.21
= 37.675 g
Sn
O
29.67 g
37.68 - 29.67
= 8.01 g
mole
0.25
0.5
Ratio
1
2
Empirical formula is SnO2.
(ii)
4
2ZnO + C
SnO2 + C
2
2Zn + CO2
Sn + CO2
1
1
(c)
The iron corrodes.
Iron is more reactive than tin. / Iron loses electron more rapid than tin
So iron(II) ion is formed and reacts with oxygen and water in air resulting in rusting.
1
1
(a)
Non-rechargeable cell
1
(b)
small in size / lightweight / give a constant voltage over discharge
(accept any reasonable answers)
1
(c)
(i)
1
(1)
methyl orange, change from red to orange/
Phenolphthalein, change from colourless to pink.
(ii) number of mole of NaOH used
Number of mole of excess HCl before dilution
Number of mole of HCl react with KOH
Mass of KOH = 0.009 x (39.1 + 1 + 16)
(d)
= 0.5 x 0.0455 = 0.2275 mol
= 0.2275 x 4 = 0.091 mol
= 0.1 – 0.091 = 0.009 mol
= 0.505 g
Test the solution with pH paper.
The pH paper turn blue indicating the presence of OH- ion.
or
dissolve the electrolyte in NH4NO3 solution and warm it.
Gas bubble evolves and turn moist red litmus paper blue.
(NH4+ + OHNH3 + H2O)
3
1
1
(1)
(1)
(any pH indicator method or
adding acid or
any method testing the alkaline properties of OH- with reasonable result.)
DSE-CHEM-3
3
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HKDSE Mock Exam
Marking Scheme
Marks
5
(a)
Addition reaction/ chlorination.
1
(b)
F2/ Br2
Belongs to the same group with Cl2. They has similar chemical properties.
1
1
(c)
(If choose F2) F2, F2 is more reactive than Cl2
(If choose Br2) Cl2, Cl2 is more reactive than Br2
1
(1)
(d)
(i)
Polyethene / polythene.
1
Making bottle / plastic bag / grocery bags / squeezable bottles / wrapping /
1
(other reasonable uses)
(ii)
1
6
(a)
Silver nitrate/ Silver sulphate
1
(b)
Correct. Ag+ is stronger oxidizing agent Cu2+ so Ag+ ion is preferentially discharged. /
1
Ag is less reactive than Cu so Ag+ has higher tendency to gain electron.
(1)
(c)
Ag(s)
Ag(s)
(d)
Measure the conductivity of the solution.
1
+
The conductivity is constant if the [Ag ] is constant.
(e)
1
number of mole of Ag plated = 0.15 mol
Number of mole of electron consumed = 0.15 mol
Number of electron consumed = 0.15 x 6.02 x 1023 = 9.03 x 1022
DSE-CHEM-4
2
4
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HKDSE Mock Exam
Marking Scheme
Marks
7
(a)
1
(Branched chain or ring chain are not accepted)
C15H28(s)
(b)
(c)
+
22O2(g)
15CO2(g)
+ 14H2O(l)
1
They do not belong to same homologous series because they have different general
formula /
1
C10H20 contain C=C double bond but C5H12 does not.
(1)
(i)
1
Fuel oil is not easy burned. Less valuable
(ii)
3
(
1 mark for correct set-up;
1 mark for correct gas collection method;
1 mark for labelling of pentacosane and porous granules;
award 0 mark if the set-up is not workable )
(iii) standard enthalpy change of cracking of pentacosane
= +1036 kJ mol-1
DSE-CHEM-5
3
5
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HKDSE Mock Exam
Marking Scheme
PART II
Marks
8
(a)
Gas is collected in the syringe. /
1
The temperature of solution raise. (exothermic process)
(1)
(b)
0.072 dm3 / 72 cm3
3
(c)
Plot a graph of the volume of oxygen collected against time.
1
Draw a tangent on the curve at particular time,
(d)
9
(a)
the slope of tangent is the rate of reaction at particular time.
1
Y:
Use same volume but higher concentration of H2O2.
1
Z:
Carry out the experiment at a lower temperature.
1
(i)
1
(ii)
1
(b)
(c)
CH3Cl has higher boiling point than BH3
1
CH3Cl is polar while BH3 is non-polar. /
1
Stronger intermolecular force exists between the polar molecule.
(1)
(i)
-Protons are added to the nucleus and electrons are added to the outermost shell
of the atoms across the period.
1
-The shielding effect due to the inner shell electrons remains almost the same.
1
-Hence the effective nuclear charge felt by the outermost shell electrons increases
across the period.
1
Outermost shell electrons are pulled closer to the nucleus. So, the atomic radii of
elements decrease.
DSE-CHEM-6
6
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HKDSE Mock Exam
Marking Scheme
Marks
(ii)
1
The atomic radii of Period 3 elements are greater as there is one more occupied
electron shell in their atoms.
1
The trend of atomic radii of elements across the two periods is similar as atomic
radii exhibit periodicity.
10
1
(a)
[H+(aq)] = 1.34 x 10-3 mol dm-3
2
(b)
44200 dm3
3
(c)
The pH decrease.
1
For endothermic reaction, high temperature favour forward reaction.
More acid molecule dissociates in high temperature and the [H+] increase.
1
11
3
DSE-CHEM-7
7
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HKDSE Mock Exam
Marking Scheme
Marks
12
1
-
Trans has higher melting point but lower boiling point than that of cis
1
-
Because trans has higher packing efficiency so stronger intermolecular force exists
1
between trans molecule in the solid state.
-
The cis molecule is asymmetric so the molecule is polar. Stronger intermolecular
1
force exists between the polar molecule in liquid state.
-
Communication mark
DSE-CHEM-8
1
8
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