Download - Public Assessment of the HKDSE Chemistry Examination...In Chemistry, students are assessed by their teachers on their performance of a wide range of skills involved in practical and

Public Assessment of the HKDSE Chemistry Examination

1.PublicAssessmentThe public assessment of the Hong Kong Diploma of Secondary Education (HKDSE) Chemistry Exam consists of a public examination component and a school-based assessment component.

A. PublicExaminationcomponentIn Chemistry, the mark of the public examination component contributes 80% of the final subject mark.

Paper Section Question types Weighing Duration Curriculum

Paper 1Section A Multiple-choice Questions 18%

2 hours 30 minutes Compulsory PartSection B Short Questions and Structured / Essay-type Questions 42%

Paper 2 – Structured Questions 20% 1 hour Elective Part (2 out of 3)

B. School-basedAssessmentcomponentIn Chemistry, students are assessed by their teachers on their performance of a wide range of skills involved in practical and non-practical related tasks throughout S.5 and S.6. The mark of the school-based assessment component contributes 20% of the final subject mark.

Year of examination Assessment types Weighing2012 and 2013 Practical related component 20%

Starting from 2014Practical related component 16%

Non-practical related component 4%

2.Standards-referencedReportingThe HKDSE makes use of standards-referenced reporting, which means candidates’ levels of performance will be reported with reference to a set of standards as defined by cut scores on the variable or scale for a given subject. The following diagram represents the set of standards for a given subject:

Cut scores

U 1 2 3 4 5

Variable/scale

Within the context of the HKDSE there will be five cut scores, which will be used to distinguish five levels of performance (1–5), with 5 being the highest. The Level 5 candidates with the best performance will have their results annotated with the symbols ∗∗ and the next top group with the symbol ∗. A performance below the threshold cut score for Level 1 will be labelled as ‘Unclassified’ (U).

– II –

Exam StrategiesA. TimeAllocation

Paper1(CompulsoryPart)——2hours30minutes

Section Suggested Time Allocation Approximate Time per Question

A 45 minutes 1 – 1.5 minutes

B 105 minutes 5 – 10 minutes

– Allow 5 minutes for final checking.

Paper2(ElectivePart)——1hour

Time Allowed Approximate Time per Question

60 minutes (answering 2 out of 3 questions) 25 – 30 minutes

– Allow 5 minutes for final checking.

B. AnsweringSkills

Paper1A Multiple-choiceQuestions

• Make your draft next to each question so that the draft can be referenced during final checking.• Mark only ONE answer for each question.• The statements in the options may be misleading. DO NOT spend too much time in reading the options.• DO NOT leave any questions unanswered even if you do not know the answer. Eliminate the incorrect

options to choose the answer or even use wild guessing, if and only if you have no idea about the answer.

Paper1BandPaper2 ShortQuestionsandStructured/Essay-typeQuestions

• Skip the questions that you do not have confidence on. Go back to those questions after you have finished the others.

• The chemical equations written should be balanced. The state of the substances should also be written if possible.

• In answering questions involving calculations, show your steps rather than just writing down the answers. In case you do not get the correct answer, you can get marks for the correct methods used.

• Pay attention to the units in calculation, especially in the calculation of molarity and concentration.• In answering questions involving drawing:

– Always use a pencil.– Draw exact and precise figures with tools like rulers and protractors.– Choose an appropriate scale.– Label significant items like the chemicals and apparatus used.

• Pay attention to the question commands:– ‘Write’ – you are supposed to write down the answer only without reasoning.– ‘Explain’ – you should answer the question in detail.

• In answering an essay-type question:– The answer must be in paragraph form.– State the key points of the answer clearly with specific terminology.– Draw diagrams to help the explanation if necessary.

– III –

Common Mistake Analysis1. Thechemicalequationisnotbalanced.

E.g.: Write the chemical equation for the reaction between copper and acidified potassium permanganate.

Wrong answer: Cu(s) + KMnO4(aq) + H

+(aq) → Cu2+(aq) + Mn2+(aq) + K+(aq) + H2O(l)Correct answer: 5Cu(s) + 2KMnO4(aq) + 16H

+(aq) → 5Cu2+(aq) + 2Mn2+(aq) + 2K+(aq) + 8H2O(l)

2. Inansweringaquestioninvolvecalculation,theunitoftheanswerisnotgiven.E.g.: 58.5 g of sodium chloride is dissolved into 1 dm3 of water. Calculate the concentration of the

solution.

Wrong answer:

Concentration of the solution =

58 523 0 35 5

1

.. .+ = 1

Correct answer:

Concentration of the solution =

58 523 0 35 5

1

.. .+ = 1 M

3. Theconceptsofthestructureandtherepeatingunitofapolymeraremixedup.E.g.: Draw the repeating unit of polyethene.

Wrong answer:

Correct answer:

4. In‘ChemicalReactionsandEnergy’,the‘-’signismissingfortheenthalpychangeofanexothermicreaction.E.g.: When 1 mole of carbon is completely burnt in air, 393.5 kJ mol-1 of heat is evolved. Which of the

following may be the standard enthalpy change of formation of carbon dioxide?A. 393.5 kJ mol-1

B. 787.0 kJ mol-1

C. -393.5 kJ mol-1

D. -787.0 kJ mol-1

Wrong answer: ACorrect answer: C

– V –

2012 HKDSE Exam and Mock Exam Questions DistributionPaper1(CompulsoryPart)

Paper 1A consists of Part I (24 MC questions) and Part II (12 MC questions).

Paper 1B consists of Part I (56 marks) and Part II (28 marks).

Distribution of Exam Questions:

Topics2012 HKDSE Mock 1 Mock 2 Mock 3 Mock 4 Mock 5 Revision Test

Section A Section B Section A Section B Section A Section B Section A Section B Section A Section B Section A Section B Section A Section B

I. Planet earth — — — — 2 — — — — — — — 1, 15 1

II. Microscopic world I 1, 8, 15 1 8, 16 2 5, 6, 10, 15 8 2, 9, 17 2 1, 2, 9 6 1, 3, 9, 13, 19, 23

2 8, 13, 30, 31 4, 7

III. Metals 3, 9, 16, 23 7, 9 5, 10, 13, 18, 23

3 4, 12, 18, 19 3 3, 6, 8 1 6, 8, 23, 24 3 4, 7, 8 1 10, 16, 18, 22, 23, 36

5

IV. Acids and bases 2, 4, 10, 19, 20

6 4, 9, 15, 20, 21

4, 7 3, 7, 8, 16, 22

2, 7 1, 4, 15, 16, 22, 24

4, 7, 10 10, 15, 19, 21, 22

1, 8 5, 6, 18, 24 9 4, 9, 11, 12, 19, 20

6, 9

V. Fossil fuels and carbon compounds

11, 17, 21, 24 2, 10 2, 7, 19, 22, 24

6 1, 9, 11, 17 1 10, 11, 19, 21, 23

8, 11 3, 5, 12, 16, 17

7, 10 14, 15, 20, 22

4, 6, 8 2, 7, 26, 34 2, 10, 12

VI. Microscopic world II 5, 12 4 11 1 20 5 7 3 11 2 2 5 5, 35 3

VII. Redox reaction, chemical cells and electrolysis

6, 13, 18, 22 3, 5 1, 3, 12, 17 5, 8 13, 14, 21, 24

4, 9 5, 12, 14, 20 6, 9 4, 7, 18, 20 5 11, 12, 17, 21

7 3, 17, 21, 25, 28, 33

8, 11

VIII. Chemical reactions and energy

7, 14 8 6, 14 9 23 6 13, 18 5 13, 14 4, 9 10, 16 3, 10 6, 14 13

IX. Rate of reaction 25 11 26, 33, 35 10 26, 31 14 28 12 29, 32 12 26, 33, 34 12 24, 27 14

X. Chemical equilibrium 26, 27, 35 13 29, 31 15 28, 30, 32 10 25, 26, 29, 35

17 31, 33, 36 13 29, 35 14 29, 32 15

XI. Chemistry of carbon compounds

28, 29, 32, 33, 34, 36

12, 14, 15 25, 28, 30, 32, 34, 36

12, 13, 14 25, 27, 29, 33, 34, 35

11, 12, 13 27, 30, 31, 32, 34, 36

13, 14 25, 26, 28, 30, 34, 35

11, 14, 15 25, 27, 28, 30, 31, 36

11, 15, 16 — —

XII. Patterns in the chemical world

30, 31 16 27 11 36 15 33 15, 16 27 16 32 13 — —

About 70% of the questions are set at the former HKCE Examination level. The rest (30% of the questions) are

set at the former HKAL Examination level.

Paper2(ElectivePart)

Paper 2 consists of three questions (20 marks each). Candidates should answer two questions.

– VI –

Useful FormulaeMicroscopicWorld:Atomic number = Number of protonsMass number = Number of protons + Number of neutrons

Relative atomic mass = Average relative isotopic mass of the element12

×× Mass of an atom of carbon-12

Moleandconcentration:

Number of moles = Mass of the substance in g

Molar mass in g mol-1 =

Number of particlesAvogadro’s number

Percentage by mass of an element in a compound

= Atomic number of an element × Number of an element in the compound

Formula mass of the compound × 100%

Concentration (g dm-3) = Mass of solute in g

Volume of solution in dm3

Concentration (M or mol dm-3) = Number of moles of solute

Volume of solution in ddm3

Rateofreaction:

Rate of reaction = D[reactant]

Dt or

D[product]Dt

Under the same temperature and pressure, Number of moles of gas = Volume of gas

Molar volume of gas

ChemicalEquilibrium:

For a reversible reaction aA + bB cC + dD, Kc = [C] [D]

[A] [B]

eqmc

eqmd

eqma

eqmb

.

– VIII –

– 135 – © 2012 Hong Kong Educational Publishing Co.

4.

Which of the following combinations would produce the largest current flowing from metal P to metal Q in the external circuit?

Metal P Metal Q

A Mg Ag

B. Ag Na

C. Ag Zn

D. Zn Cu

5. Which of the following statements concerning propene is/are correct?

(1) It can be oxidized by K2Cr2O7/H+ solution.

(2) It can undergo addition polymerization.(3) It can be prepared by the catalytic cracking of a saturated hydrocarbon.

A. (1) only

B. (3) only

C. (2) and (3) only

D. (1), (2) and (3)

6. The experiment is carried out to find the order of metal reactivity of four metals.

MetalMetal ions

Mg2+ Al3+ Pb2+ Cu2+

Mg ✗ ✓ ✓ ✓Al ✗ ✗ ✓ ✓Pb ✗ ✗ ✗ ✓

What is the order of metal reactivity in ascending order?

A. Mg Cu Pb Al

B. Pb Cu Al Mg

C. Mg Al Cu Pb

D. Mg Al Pb Cu

MOCK 4 PAPER 1A-3

Answers written in the margins will not be marked.

Ans

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the

mar

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will

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be

mar

ked.

Ans

wer

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will

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ked.

– 111 –

Please stick the barcode label here.

Page total© 2012 Hong Kong Educational Publishing Co.

6. The following set-up is used to carry out electrolysis:

(a) (i) What material is suitable for making electrode X? Explain your answer.

(ii) What is observed around electrode X?

(3 marks)

MOCK 3 PAPER 1B-7


Section B Materials Chemistry

Answer ALL parts of the question.

2. (a) Cellulose is a natural polymer in plants. Its structure is shown below.

(i) Name the monomer of cellulose and the reaction type of making cellulose from its monomers.(1 mark)

(ii) (1) Name the type of reaction between cellulose and concentrated H2SO4.

(2) Write the related chemical equation in (1).(2 marks)

(iii) (1) Cellulose can undergo esterification with ethanoic acid. Explain why it is possible.

(2) Name and draw the product formed in (1).(3 marks)

(iv) Comment on the following statements.

(1) Cellulose is a biodegradable polymer.

(2) Cellulose is insoluble in water, but it can absorb water.(4 marks)

MOCK 3 PAPER 2-4


This paper consists of two sections. There are 36 multiple-choice questions in Section A and 15 conventional questions in Section B.

Section A

1. Which of the following is a usage of quicklime?

A. making steel from iron

B. neutralizing the SO2 from power stations

C. constructing buildings

D. extracting iron from iron ore

2. Upon cracking, one molecule of the alkane C12H26 gives ethene and propene in the ratio of 2 : 1 and an alkane X. What is the molecular formula of X?

A. C2H6B. C5H12C. C8H16D. C9H20

3. Consider the following diagram about the set-up of a simple chemical cell.

According to the above diagram, which of the following statements is correct?

A. The lead electrode is the positive pole.

B. The lead electrode will dissolve.

C. Sugar solution can be used as the electrolyte.

D. Lead is at a higher position in the electrochemical series than metal Y.

Revision Test-2


Section B

1. ‘The major composition of coral is calcium carbonate.’

A student wants to confirm this statement by experiments. His teacher provides him with dilute hydrochloric acid and simple laboratory apparatus.

(a) (i) Suggest a test to show the presence of calcium in coral.(ii) State the observation of the experiment.

(2 marks)

(b) A colourless gas is evolved when a piece of coral is put into hydrochloric acid.(i) Suggest a test to identify the gas.(ii) Write the chemical equation for the reaction in (b) (i).

(2 marks)

2. The structure of a polymer is shown below:

(a) What is the meaning of the term ‘polymer’?(1 mark)

(b) (i) Name the type of polymerization for forming the above polymer.(ii) Name the monomer of the above polymer.

(2 marks)

(c) Suggest ONE usage of the above polymer.(1 mark)

(d) Write the empirical formula of the above polymer.(1 mark)

3. (a) Draw the 3-D structure of NH3.(1 mark)

(b) Is NH3 a polar molecule? Explain your answer. (2 marks)

(c) (i) Besides van der Waals’ forces, what intermolecular forces are formed within NH3 molecules? (ii) State the TWO conditions for forming the intermolecular forces in (c)(i).

(3 marks)

Revision Test-13

Mock Exam 2


27. BIn A, protein is an amide.\ A is incorrect.In C, glucose is an aldehyde.\ C is incorrect.In D, aspirin is an ester.\ D is incorrect.

28. A2NO(g) + O2(g) 2NO2(g) Concentration of NO(g) after the reaction mixture is at equilibrium= (0.6 - 0.2) ÷ 2 = 0.2 dm3 mol-1

Concentration of O2(g) after the reaction mixture is at equilibrium

= 0 612

0 2 2. .− ×

÷

= 0.25 dm3 mol-1

Concentration of NO2(g) after the reaction mixture is at equilibrium= 0.2 ÷ 2 = 0.1 dm3 mol-1

\ Kc = ( . )

( . ) ( . )0 1

0 2 0 25

2

2

29. B

30. C

31. C2NaN3(s) → 2Na(s) + 3N2(g)The ratio of NaN3 and N2 formed is 2 : 3. No. of moles of 15 g of NaN3

= 15

23 3 14+ ×= 0.2308 mol No. of moles of N2 gas formed

= 32

× 0.2308

= 0.3462 mol Volume of gas formed= 0.3462 × 24.0= 8.3 dm3

32. BFor condition (1), it favours the reaction that the total number of gas molecules is decreased.For condition (2), it favours exothermic reactions.In B, it is an exothermic reaction, and the number of molecules decreases from 4 units to 2 units.\ B is correct.

Concentration

= no. of moles of solute

Volume of the container

For aA bB cC dD+ +

KC D

A Bceqmc

eqmd

eqma

eqmb=

[ ] [ ]

[ ] [ ]

where Kc is a constant.

Find the functional group

of the starting material and

product first.

The molar volume for all the

gases is 24 dm3.

Chemistry: Mock Exam Papers Second Edition Solution Guide


9. Chemical cell and electrolysis are the examples. Similarity:

They both contain two electrodes. 1OR They are both redox reactions. (1)Differences:Chemical cell: It gives out electrical energy. 1Electrolysis: It consumes electrical energy.

Compare the structures of and the chemical reactions happenning inside the two devices.

9. Chemical cell and electrolysis are the examples. Similarity:

They both contain a cathode, an anode and an electrolyte. 1OR The reduction occurs at the cathode and oxidation occurs at the anode. (1)Differences:Chemical cell: It converts chemical energy to electrical energy. 1 The redox reaction occurs spontaneously. 1OR The cathode is the positive pole and the anode is the negative pole. (1)OR It generates electricity from chemical changes. (1) (Any two)Electrolysis: It converts electrical energy to chemical energy. 1 The redox reaction is forced to occur. 1OR The cathode is the negative pole and the anode is the positive pole. (1)OR The electrolytes are decomposed by electricity. (1) (Any two)Effective communication 1

10. (a) Vapour of alkanes with low relative molecular mass condense at lower temperature. 1

(b) Thermal cracking: heating under pressure in the absence of air 1OR Catalytic cracking: heating in the presence of catalyst in the absence of air (1)

(c) This is because it has higher carbon content / it burns incompletely. 1

(d) Use low sulphur coal instead of high sulphur coal / installation of scrubbers 1

The candidate’s responses

show a basic knowledge

about chemical cells and

electrolysis. The candidate

fails to point out the similarity

and differences precisely.

T h e e x p l a n a t i o n s a r e

incomplete or wrong.

*

*The candidate’s responses

show a comprehens ive

understanding of chemical

c e l l s a n d e l e c t ro l y s i s .

The candidate can give a

detailed comparison with the

use of specific terminology.

Download - Public Assessment of the HKDSE Chemistry Examination...In Chemistry, students are assessed by their teachers on their performance of a wide range of skills involved in practical and

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