香港中學文溉考試
HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION
練習卷
PRACTICE PAPER
化學
試卷一
CHEMISTRY PAPER 1
MARKING SCHEME
SECTION A
Part I
Question No.
K ey
23.
B D AD C B B C B B B AA C D AD AC C B AD D
Question No.
Key
25.
A
I.
2
3,
4,
5,
6
7,
8,
9
10
II.
12
13
14.
15
16.
17.
18.
19
20.
21.
22.
24
Part II
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
PP-DSE-CHEM 1-2
D AB C AD B D C B C
26.
SECTION B - Provisional Marking Scheme
General Notes for Teachers on Marking
I.
The marking scheme is the preliminary version before the normal standardisation process and some revisions
may be necessary after actual samples of performance have been collected and scrutinised by the HKEAA.
Teachers are strongly advised to conduct their own internal standardisation procedures before applying the
marking schemes. After standardisation, teachers should adhere to the marking scheme to ensure a uniform
standard of marking within the school.
2.
The marking scheme may not exhaust all possible answers for each question. Teachers should exercise their
professional discretion and」udgment in accepting alternative answers that are not in the marking scheme but
are correct and well reasoned.
3.
The following symbols are used:
A single slash indicates an acceptable alternative within an answer.
＊
1.
Step-mark (for questions involving calculations)
Correct spelling required
4.
In questions as如ng for a specified number of reasons or examples etc. and a student gives more than the
required number, the extra answers should not be marked. For instance, in a question asking students to
provide two examples, and if a student gives three answers, only the first two should be marked.
5.
For questions involving calculations, the number of significant figures in candidates'final answers should
tally with that given in the question
6.
In the question paper, questions which assess candidates'communication skills are marked with an asterisk
(*). For these questions, the mark for effective communication (I mark per question) will be awarded if
candidates can produce paragraph-length answers which are easily understandable. No marks for effective
communication will be awarded if the answers produced by candidates are written in note form, and/or
contain a lot of irrelevant materials
PP-DSE-CHEM 1-3
Part I
1.
(a) (i)
or,
(ii)
。
ZnO + H2S04 --->ZnSO己比0
Zn0+2W---> Zn2+ +H2
M
1
(1)
Unreacted ZnO(s) can be seen
(iii) To ensure that the product is not contaminated with sulphuric acid.
or, The unreacted ZnO(s) can be removed by filtration, but it is difficult to remove the
excess H2S0,(aq).
1
(1)
(3)
(b) Remove a drop of the solution with a glass rod, and see whether any solid forms when the
drop cools.
(Accept other correct answers.)
(I)
(c) Washing with distilled water can remove the water-soluble impurities
Using a small amount of water helps reduce loss of the salt.
PP-DSE-CHEM I-4
｀
丿
l
I(
(e) Zn/ Zn(OH)z I ZnC03
＇
,
`
J、
`
、
l1
1(
（
(d) Any ONE of the following:
- drying the crystals between filter papers
- putting the crystals in a desiccator.
(DO NOT accept methods which involve strong heating.)
M
2. (a) Some components of wine (substances with a pleasant odour) can be Qi;i中sed bv oxvgen m
血to give products that have a flat taste.
or, Ethanol.m wme can be 0XIdu;ed bv oxvgen in air to ewe ethanal lethanoIC acU.
(b) (i)
The outermost shell of an argon atom is a�- :. Ar does not readily
form bonds with other atoms.
(ii)
Ar is denser than air. It�. and thus prevents the wine from
contact with air.
（1)
(1)
(iii) He is�. It will not displace air/ it will easily diffuse from the bottle
(c) The substances with a pleasant odour are�- Pumping air out from
the bottle may also remove these substances
(l)
PP-DSE-CHEM 1-5
Marks
3. (a) (i)
寸
or,
曰］。［
Mg3N2 + 6比0 ➔3Mg(OH), + 2NH3
No. There is no change in oxidation number of any atom.
(1)
）
3
］（
(ii)
Mgr]O[
(b) (i)
(ii)
The nitrogen in NCJ, and that in NH 3 both have the�
and lone eIectron pairs l have three electron bond- airs and one Ione electron air in
their outermost shells.
The � causes both NCJ, and NH3 to adopt a
tetrahedral structure l trigonal pvramidal shape.
I
(3)
PP-DSE-CHEM 1-6
M
4.
(a) Dissolve 1.14 g of M 2C03(s) in some distilled water/ deionised water in a beaker. Transfer
the solution to a 100.0 cm3 volumetric flask.
）這the beaker with distilled water / deionised water and �
volumetric flask.
Add distilled water / deionised water ��
Shake the volumetric flask to ensure its content is well mixed.
(3)
(b) No. of moles of W(aq) used
= 0.085 X 25.30 X 10-3
= 2.15 X 10-3
叱C03 +2H
+
+
-->2M +co,+比0
* step mark
PP-DSE-CHEM 1-7
l＊
l的
No. of moles of M2C03 in 100 cm3 of the solution
100 1
= 2.15x10-3 X--X10 2
l.14x2
Formula mass of M2C0 3 =
0.0215
= 106
Let x be the relative atomic mass of M
2x+l2+16x3=106
x=23
M is likely to be Na.
Marks
5.
(a)
(b) � of the petroleum gaseous fraction.
or, Cracking of naphtha / heavy oil (or any appropriate petroleum fraction) followed by
� of the products.
(c) (i)
｝
1
＊
丿
、
3
1(
C
H
18.2
81.8
18.2
81.8
Atom ratio
12
I
= 6.82 : 18.2
=
:
8
3
Alkane has the general formula C,,H2,.2
:. X is propane IC乩·
% by mass
l
(1)
X: C,比easily undergoes � to give CO, and比0 The products
pose little harm to the environment.
Kerosene: kerosene undergoes � to give a luminous flame耳2
flame can be more easiIv seen.
(Accept other reasonable answers.)
(ii)
(2)
* step mark
PP-DSE-CHEM 1-8
Mru.ks
6.
(a) tpropane-1,3-diol / l,3-propanediol
I
(I)
(b) All three compounds have a hydroxyl group I are monohydric alcohols. The boiling point of
these compounds depends on the strength of van der Waals forces between molecules
The strength of van der Waals forces in alcohols increases with the carbon chain length /
relative molecular mass. Boiling point increases in the order: A < B < C
(2)
(c) For isomeric compounds with the same functional group, the�
is affected bv the shape of the molecules.
CH3C比CH20H has a linear structure. This allows the molecules to have a greater area of
contact than those of C比CH(OH)CH,. :.C比C比C比OH has a greater density
or, The non-linear structure of CH3CH(OH)C比makes the formation of H-bonds less effective
:. CH3CH(OH)CH3 has a smaller density
(I)
(d) F
The rate at which the steel balls drop depends on the �
(fricUonal force) experienced bv the ball. ThIS IS related to the intermoIecular attraction of
the liquids.
In the three compounds, the intermolecular attraction is predominately H-bond. �
H-bonds formed oer molecule is I in D. 2 in E and 3 in F..-. F is the most viscous and the
ball will drop most slowly.
or, F has the highest b.p. among the three compounds. Its intermolecular attraction is strongest
.-. The ball will drop most slowly in F
Effective communication (Award I mark if candidates express their ideas clearly.)
-i- correct spelling
PP-DSE-CHEM 1-9
(I)
I
(4)
M
7. (a) (i)
No. of moles of CaO(s) used =
= 0.053
Heat liberated= 53 x 4.2 x (46.7 -28.2)
= 4118 J
4118
AH=
0.053
= -77.0 kJ moi-1
(Acceptable range: -72.6 to -77.0 kJ moi-1)
－
、
丿
I
（
ompounds of Al are non-toxic. They�(II) Compound
Al is a good conductor of heat. The heat liberated from the reaction of CaO(s) with
比O(f) can readily be transmitted to the coffee beverage.
Aluminium is covered by a layer of unreactive Al 203(s), which prevents the metal
from corrosion.
(Accept other reasonable answers.)
）
l
3(
(b) (i) Any THREE of the fol!owing (at least 1 mark should be al!ocated to each part)
(I) PP is a poor conductor of heat. Using PP container to hold CaO(s) will protect
hands from skin burns.
PP can withstand the high temperature caused by the reaction of CaO(s) with
H2O(£)
I*
）
5
(
(ii) Any ONE of the following:
- PP is not a perfect heat insulator; heat is lost to the surroundings
- Some CaO(s) may have reacted with比O(R)in air
(Accept other reasonable answers.)
＊＊
1I
3.0
(40.1+16)
(I)
(I)
(I)
(ii) The reaction of CaO(s) and比O(£) IS hIghlv exothermIC, and CaO(s) IS an mexpenswe
material.
(Accept other reasonable answers.)
(4)
* step mark
PP-DSE-CHEM 1-10
Marks
D
(
n'
（
For'Yes'answers,
- The use of DMFC laptop computers will become prevalent when stringent
environmental laws are enforced as the disposal of DMFCs causes less harm to the
environment than other rechargeable cells / methanol is a greener fuel than
hydrocarbons.
- DMFC laptop computers will be commonly used in field work where electric sockets are
not available.
(Accept other reasonable answers.)
2
(c) Accept both'Yes'and'No'answers. Mai·ks will be awarded only to the explanation
For'No'answers,
- Electrical sockets can be found in most places. DMFC laptop computers will only be
used in places where electric sockets are not available.
- The cost for the manufacture of methanol is higher than that for the generation of
electricity in most places.
勾
l(
Toxic and flammable
n(
(ii)
丶
�
or,
The electrochemical reactions involve ions. Water, an ionisable solvent, is suitable for
use as the reaction medium.
比0 is involved in the half-equations.
(b) (ii))
2
I(
8. (a) anode : C比OH(aq) + H20(£) ➔ C02(g) + 6H\aq) + 6e­
cathode: 02(g) + 4H+(aq) + 4e- ➔ 2H20(£)
(!)
(1)
(2)
PP-DSE-CHEM 1-11
Part II
M
9. (a)
MgO
AbO3
SIO2
瓦OIO
so2
IC
IC
CN
SM
SM
BA
AM
AC
AC
AC
(2)
onic
(b) Ion
i oxides are basic, while covalent oxides are acidic.
1
(1)
(c) Add each oxide to HCl(aq) and measure the pH of the mixture. Only MgO(s) and Al凸(s)
react with HCl(aq) and the pH increases. These two oxides demonstrate bas ic properties.
Add each oxide to NaOH(aq) and measure the pH of the mixture. Only Al,03(s), Si02(s),
瓦O,。（s) and S02(g) react with NaOH(aq) (Si02(s) reacts with hot conc. NaOH(aq)), and the
pH decreases. These oxides demonstrate acidic properties.
Al203(s) reacts in both cases. It is amphoteric.
(Accept other experimental method.)
l+l
Effective communication (This mark will be awarded if candidates can clearly state the
expected results for the tests on Al203(s).)
l+l
(5)
Mat·ks
10. (a) Colorimetry/ using colorimter
(b) (i )
The rate of consumption of MnO,-(aq) ions is slow at the beginning (from Oto 180 s)
and then increases rapidly (from 200 to 340 s)
It is likely to be due to the building up of the concentration of the product which
catalyses the reaction.
(ii)
Repeat the experiment with a few drops of Mn2+(aq) firstly added to the reaction
mixture.
Consumption of MnO且aq) ions will be faster at the beginning if Mn2+(aq) is a catalyst.
PP-DSE-CHEM曰2
1
(1)
I
(4)
M
十
比
�
丶
2
I
叭
h
t
e
l
皿
A H
Li
）
1
。^ ]
,
＼
ab
。
： －一O
II.
c: excess cone. H 2S04 (or cone. H 3P04); heat
(3)
12. (a) (i)
0
後C＇
H
OH
丶C02H
H
and
。
丶cs
Marks
。
H洱
(ii) They turn the plane of polarisation of a beam of plane polarised light in opposite
directions.
or, One of the compounds is laevorotatory while the other is dextrorotatory
or, Crystals of the two compounds have different appearance
IIc
十
。
mtH [《》
u
i
t
a
。
十
g
n
R
e
p
e
的
PP-DSE-CHEM 1-13
1+1
(I)
(I)
(3)
M
13. (a)
氐＝
訂
［Cu(NH
(aq)］
[Cu 2+ (aq)] [NH 3 (aq)J4
(I)
(b)
K, =
0.08
(0.002)(0.0014) 4
= 1.04 x 10 13 (mo! dm勺4
(1 mark for answer; 1 mark for correct units)
!+!
(2)
(c)比S0.(aq) reacts with the NH3(aq) present:
H'(aq) + NH,(aq) ➔ NH訌 aq)
o r, 比S0.(aq) + 2NH 3(aq) ➔ (NH4),S0.(aq)
Removal of NH3(aq) causes the position of the following equilibrium to shift to the left.
2
Cu '(aq) + 4NH3(aq) ace Cu(NH3)/'(aq)
NI七(aq) is a weak base:
NH 3 (aq) + H20(t) ace NH訌aq) + Off(aq)
f
2
When [Cu '(aq)] builds up, it will react with the Of (aq) ions to give the blue precipitate
2
Cu '(aq) + 20ff(aq) ➔ Cu(OH),(s)
When excess比S04(aq) is added, it will react with the Cu (OH), (s) formed to give a blue
solution.
2
Cu(OH) 2( s) + 2H'(aq) ➔ Cu '(aq) + 2比O(t)
(3 marks for chemical equations; I mark for explanation of the shift in equilibrium position;
I mark for the formation of blue precipitate.)
I
(I)
1
(5)
PP-DSE-CHEM曰4
香港中學文蔥考試
HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION
練習卷
PRACTICE PAPER
化學試卷二
CHEMISTRY PAPER 2
評卷參考
MARKING SCHEME
Provisional Marking Scheme
General Notes for Teachers on Marking
J.
The marking scheme is the preliminary version before the normal standardisation process and some revisions
may be necessary after actual samples of performance have been collected and scrutinised by the HKEAA
Teachers are strongly advised to conduct their own internal standardisation procedures before applying the
marking schemes. After standardisation, teachers should adhere to the marking scheme to ensure a uniform
standard of marking within the school.
2.
The marking scheme may not exhaust all possible answers for each question. Teachers should exercise their
professional discretion and」udgment in accepting alternative answers that are not in the m 訌king scheme but
are correct and well reasoned.
3.
The following symbols are used:
A single slash indicates an acceptable alternative within an answer.
＊
1.
Step-mark (for questions involving calculations)
Correct spelling required
4.
In questions asking for a specified number of reasons or examples ete. and a student gives more than the
required number, the extra answers should not be marked. For instance, in a question asking students to
provide two examples, and if a student gives three answers, only the first two should be marked.
5.
For questions involving calculations, the number of significant figures in candidates'final answers should
tally with that given in the question
PP-DSE-CHEM 2-2
Marks
I.
(a) (i)
Any ONE of the following:
- Reichstein process is used for synthesising vitamin C, which is in great demand as it
cannot be synthesised in human body.
- Reichstein process provides a synthetic route to convert D-Glucose, a sugar which is
highly abundant and cheap, to !.-ascorbic acid.
- The enzymatic reaction in Reichstein process inverts the sugars from D- to Lisomer.
- Reichstein process provides insight on the use of protecting groups in organic
synthesis.
(Accept other reasonable answers.)
I
(I)
(I)
(I)
(I)
(!)
(ii)
treduction I catalytic hydrogenation
_!
(I)
Commonly used ox汕sing agents will also oxidise the other hydroxyl groups in D­
sorbitol / are not selective as compared with the enzyme.
or, The enzyme can selectively oxidise the second -OH group in D-sorbitol to give Lsorbose.
(iii) (!)
(iv) This method uses a catalyst (the enzyme ) instead of stoichiometric reagents
It uses less hazardous chemicals (e.g. MeOH / acid).
、
�
、
丿2
2
,
＇
、 II (
Any ONE of the following:
- The rate of reaction is proportional to the concentration of the reactant
- The half-life of the reaction is constant.
、
·
'1
）1
）
1
l(
（（
(II) At pH<4 or pH>6, the enzyme will undergo denaturation / the (tertiary/secondary)
structure of the enzyme will change leading to loss of catalytic activity
(I)
(b) (i)
(ii)
log k = constant T
kl1O`
!IT
logk
t correct spelling
PP-DSE-CHEM 2-3
Ea
2.3RT
313
27.0
3.195 X 10-3
-1.569
323
35.4
3.096 X 10-3
-1.451
333
50.4
3.003 X 10-3
-1.298
343
65.4
2.915 X 10-3
-1.184
I.
(b) (ii)
M
I
Graph of log k against ::
T
1
-1 磗29
e
2
0.0031
0.003
0.0033
0.0032
·l.2
1.3
笞
一
·l.4
幺
－
y =-1401.& + 29029
R2 =0.9962
-1.5
· l.6
-1.7
lrr
I
(I mark for the graph; I mark for the labels)
Ea
Slope: -1402 = _
2.3R
Ea = 1402 X 8.31 X 2.3
= 26.8 kJ moi-'
(Acceptable range: 24.5 to 29.0 kJ mor')
or,
土
E
In k = constant－一4
RT
lIT
Ink
kl
313
27.0
3.195 X 10-3
-3.612
323
35.4
一3
3.096x 10
-3.341
333
50.4
一
3.003 X 10 3
-2.988
1
Graph of ln k against 一
T
-2
·2O
·2.4
-2.6
"'-2.8
．薛 。．003
343
65.4
2.915 X 10-3
-2,727
(])
( 2)
0.003 l
0.0032
0.0033
．邰
荳 ｀3
y=·3227 4x+ 6 41
R2 =0.9962
-3.2
-3.4
-3.6
-3.8
ln
(I mark for the graph; I mark for the labels)
E
Slope : -3227 =-－色
R
尻＝3227 X 8.31
= 26.8 kJ mor'
(Acceptable range: 24.5 to 29.0 kJ mol-1)
PP-DSE-CHEM 2--4
(!)
(!)
(5)
M
J.
(c) (i)
、丿
丿l
丶
l
l(
（
Cl2(g) + 2Na0H(aq) ➔ NaOCl(aq) + NaCI(aq) + H20(f)
f
Cl,(g) + 20f (aq) ➔ Ocr(aq) + Cr(aq) + H,0(£)
丿
、
5
,
＼
(ii)
or,
At the cathode, ti+(aq) is preferentialJy discharged because W occupies a lower
+
position than Na in the electrochemical series.
一
2H\aq) + 2e ➔比(g)
At the anode, Cr(aq) is preferentiaJJy discharged because its concentration is high
2Cr(aq) ➔ CJ2(g) + 2 eThe membrane only alJows cations to pass through it
As there is a higher concentration of cations in the anode compartment (because anions
are removed), there will be a net flow of Na+(aq) ions from the anode compartment to
the cathode compartment, and concentrated NaOH(aq) is formed
(iii) Accept both'Yes'and'No'answers
For'No'answers,
- The production of H2 in chloroalkali industry requires the use of electricity, which is
commonly generated by burning fossil fuel (a ma」or source of air pollutants)
- CJ,(g) is the main product of the chloroalkali industry. Large scale production of
H 2(g) will yield surplus Cl2(g). The disposal of the unused CI,(g) is costly and will
cause air pollution problems
For'Yes'answers,
- Burning ofH 2(g) gives water only.
- If there is a cheap source of electricity (e.g. photovoltaic cell), production of H2(g)
by electrolysis of brine can be a means of reducing air pollution problems
(Accept other reasonable answers.)
PP-DSE-CHEM 2-5
(1)
(1)
2.
(a ) (i)
(!)
M
tface-centred cubic
(II)
1
1
No.of atoms= 8(,'-)+6（一）
2
8
=4
(III)
Density
4x27.0
(4 O5x1O`3 x6O2x1O 23
= 2.7 g cm-3
I*
I*
(5)
(ii)
(I)
In aluminium alloys, the introduction of atoms of other elements into the lattice
causes distortion of the regular arrangement of the Al atoms.
Relative motion between layers of atoms will be hindered.
(II) Li is the least dense metal. Li-Al alloys have very low densities and are suitable
materials for making aircraft bodies.
（山） （I)
Biotite has a layered structure. The attraction force between layers is much
weaker than the attraction force between atoms within a layer.
(3)
(II) as insulator in capacitors
(2)
(b) (i)
(I)
CH=CH2
V
(II) injection moulding
(2)
(ii)
(I)
SAN, in general, is not made from styrene and acrylonitrile in 1: 1 mole ratio
The two types of monomers distribute randomly along the polymer molecule
(II) In PS, the polymer molecules are attracted to each other by weak van der Waals
forces.
Acrylonitri!e has a polar-CseN group
The -OeN groups hold the polymer molecules together by stronger dipole-dipole
interaction.
t correct spelling
* step mark
PP-DSE-CHEM 2-6
(5)
Marks
2.
：：
： ：
(b) (iii) The copolymer is a� with the following structure
...— CH-CH2
… — <;:H-CH2
-CH2 一...
一 CH
一 CH-CH2 一 CH 一 CH2 —
.
... 一CH-CH2 一 CH-CH2 —...
I
(Accept other correct representations of the above su·ucture.)
The cross-linkages make the copolymer hard and rig這 As the copolymer has a giant
covalent network structure, it does not melt upon heating
(3)
PP-DSE-CHEM幻
M
3. (a) (i)
(ii)
carboxylic acid/ carboxyl group (because Xis soluble in NaOH(aq))
(Also accept phenol.)
tseparating funnel
1
(1)
丿）
、
1
(
l3(
(iii) Step 1 : Allow Xto dissolve in NaOH(aq) to give (carboxylate) anions I a salt.
Step 2 : Allow the non-polar impurities to dissolve in hexane while the (carboxylate)
anions I salt to stay in the aqueous layer.
or,
Separate the non-polar impurities (in hexane) from the salt of X
Step 3: Regenerate the (carboxylic) acid (which is insoluble in water) by adding acid
(iv) Xpossesses a C;C bond because it decolourises Br, in C比Cl3 .
In the mass spectrum, the peak at m/z; 77 shows that Xcarries a benzene ring (mlz for
c6國ion; 77)
The peak at m/z; 148 is due to the molecular ion.
The peak at m/z; 103 is due to the cation formed from the molecular ion by stripping
off a-CO洱
Possible structures of X:
C02
:
HI
了CO
2H
(5)
(v)
(I)
- The
�
spots will appear brown.
or,
�- The stationary phase is fluorescent while the two
spots are not.
(Accept other correct answers.)
(II)
Rf,=
(I)
distance travelled by X
distance travelled by solvent
9.5
(50-3-2.5)
＝ 主主
44.5
=0.21
(III) column chromatography (using the same moving phase and stationary phase)
(3)
t correct spelling
PP-DSE-CHEM 2-8
M
3.
(b) (i)
(ii)
Wash the precipitate thoroughly with deionised water
Dry the precipitate in an oven I ensure that the precipitate is dried before it is weighed
I
(2)
2+
Ba (aq) + so/-(aq) ➔ BaS04(s)
No. of moles of Ba2+ present =
0.291
(137.3+32.1+ 16x4)
1＊
= l.25x!0-3
Mass of Ba in the sample = l.25x10-3 xl37.3
=0.171
0.171
% by mass of Ba in the sample = �
0.305
=56.1
(Acceptable range: 56.0 to 56.4)
(iii) Any TWO of the following:
- The reaction must be significantly complete, i.e. the precipitate is practically
insoluble/ has a very small K,, value.
- The product ( precipitate) should have definite chemical composition.
- The rate of reaction must be fast enough to be practical.
- There must be a phase change so that the product can be separated from the reaction
mixture.
*step mark
PP-DSE-CHEM 2-9
I*
( 3)
2
(I)
(1)
(I)
(I)