Al Chemistry 2002 Paper 1

Candidate Number

2002-AL CHEM

Centre Number

PAPER 1

Seat Number HONG KONG EXAMINATIONS AUTHORITY HONG KONG ADVANCED LEVEL EXAMINATION 2002

CHEMISTRY A-LEVEL PAPER 1 Question-Answer Book 8.30 am – 11.30 am (3 hours) This paper must be answered in English

1.

There are THREE sections in this paper, Section A, Section B and Section C.

2.

Section A carries 60 marks, Section B carries 20 marks, and Section C carries 20 marks.

3.

All questions in Sections A and B are COMPULSORY. Answers are to be written in this Question-Answer Book. If you use supplementary answer sheet(s) for these two sections, write your Candidate Number on each sheet and fasten them with string to this Question-Answer Book.

4.

Answer ONE question in Section C. Answers are to be written in the AL(D) Answer Book.

5.

Write your Candidate Number, Centre Number and Seat Number in the spaces provided on this cover.

6.

Some useful constants and a Periodic Table are respectively printed on pages 18 and 19 of this Question-Answer Book.

Marker’s Use Only

Examiner’s Use Only

Marker No.

Examiner No.

A1 A2 A3 A4 A5 A6 A Total

B7 B8 B Total

Checker’s Use Only

香港考試局

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Checker No. A Total B Total

SECTION A Answer ALL questions in this Section. Write your answers in the spaces provided. 1.

(a)

The pH of human blood is maintained within a narrow range from 7.35 to 7.45 by a natural buffer system consisting of carbonic acid, H2CO3(aq), and hydrogencarbonate ions, HCO3– (aq). (i)

A buffer solution containing H2CO3(aq) and HCO3– (aq) in equal concentrations has a pH of 6.10. Calculate the dissociation constant, Ka , for H2CO3(aq).

(ii)

Calculate the ratio of concentrations of HCO3– (aq) and H2CO3(aq) in blood at pH 7.40.

(iii)

(I)

Would the blood pH of a person increase or decrease in the course of physical exertion ? Explain your answer.

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1.

(a)

(iii)

(II)

Briefly explain why the H2CO3(aq) / HCO3– (aq) buffer system can maintain the blood pH.

(7 marks) (b)

You are provided with the following standard reduction potentials: __

Eo / V

Fe2+(aq) + 2e–

Fe(s)

– 0.44

Sn2+(aq) + 2e–

Sn(s)

– 0.14

4OH–(aq)

+ 0.40

　 –

O2(g) + 2H2O(l) + 4e

　 (i)

Show, from the above information, that the corrosion of iron is spontaneous.

(ii)

‘Tin cans’ made from tin-coated iron sheets are widely used in the food industry. Will rusting occur if the tin coating is scratched ? Explain your answer.

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2.

(a)

A closed system consisting of a mixture of N2O4(g) and NO2(g) is allowed to attain equilibrium at 350 K and 700 kPa. The mixture has a light brown colour. N2O4(g) 　 2NO2(g) pale yellow brown (i)

The mixture is known to contain 46 mol % of N2O4(g). dissociation of N2O4(g) at 350 K and 700 kPa.

(ii)

Describe the colour change of the mixture when its temperature is increased under the same pressure. Explain your answer.

Calculate Kp for the

(4 marks)

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2.

(b)

An experiment was carried out to study the acid-catalysed bromination of propanone at 298 K. CH3COCH3(aq) + Br2(aq)

H+(aq)

CH3COCH2Br(aq) + HBr(aq)

The table below lists the results of the experiment.

Initial concentration / mol dm–3

Initial rate / mol dm–3 s–1

[CH3COCH3(aq)]

[Br2(aq)]

[H+(aq)]

0.30

0.050

0.050

5.7 × 10–5

0.30

0.100

0.050

5.7 × 10–5

0.30

0.050

0.100

1.2 × 10–4

0.40

0.050

0.200

3.1 × 10–4

0.40

0.050

0.050

7.6 × 10–5

(i)

Deduce the rate equation for the reaction.

(ii)

Calculate the rate constant for the reaction at 298 K.

(5 marks) 2002-AL-CHEM 1–5 保留版權 All Rights Reserved 2002

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3.

(a)

(i)

Write the ground state electronic configuration of a copper atom.

(ii)

Account for the following observation:

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When hydrated copper(II) hydroxide solid is shaken with deionized water, the liquid portion of the mixture is very pale blue. On the addition of an aqueous solution of ammonium chloride, the liquid portion shows no significant change in colour. However, if instead, aqueous ammonia is added, an intense blue colour is observed.

(4 marks)

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3.

(b)

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Give the oxidation states of the transition metals in the following compounds :

Fe3O4 __________________

Ni(CO)4 _________________ (2 marks)

(c)

CO2 and SiO2 are oxides of Group IV elements. (i)

Account for the fact that CO2 is a gas while SiO2 is a high melting solid under room temperature and atmospheric pressure.

(ii)

Give the hybridization state of carbon in CO2 and of silicon in SiO2.

(4 marks)

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4.

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Read the passage below and answer the questions that follow. Parallels exist between main group chemistry and organic chemistry. One of the best known of these parallels is between benzene, C6H6 , and the isoelectronic borazine (the so-called ‘inorganic benzene’), B3N3H6. All the B−N bond distances in the planar borazine ring are equal to 0.144 nm and the C−C bond distances in benzene are also 0.144 nm, indicating that the structure of borazine can be represented by a delocalized bonding scheme. Some of the similarities in physical properties between these two compounds are striking, as shown in the table below. However, their chemistry is different because of the difference in electronegativity between boron and nitrogen. For example, borazine reacts with hydrogen chloride gas whereas benzene does not.

Physical property

Benzene

Borazine

melting point / K

279

216

boiling point / K

353

338

0.81

0.81

–3

density / g cm

Another interesting parallel between boron-nitrogen chemistry and carbon chemistry is exemplified by boron nitride, (BN)x. Boron nitride can exist in a hexagonal form, similar to graphite. In graphite, the π-electrons are involved in an extended delocalized system and this gives rise to a high electrical conductivity. In hexagonal boron nitride, the structure is composed of layers of hexagonal B3N3 rings, which share common edges. Within a layer, the B−N distances are 0.145 nm, which is almost equal to the B−N distance in borazine. In hexagonal boron nitride, the layers lie directly over one another and are arranged so that boron and nitrogen atoms lie over each other. This contrasts with the staggered pattern found in graphite. In hexagonal boron nitride, the inter-layer separation is 0.330 nm. Unlike graphite, hexagonal boron nitride is a poor conductor of electricity. (a)

What is the physical state of borazine at room temperature ?

(1 mark) (b)

Draw the structure of a molecule of borazine, and deduce whether or not borazine possesses a net dipole moment.

(3 marks) 2002-AL-CHEM 1–8 保留版權 All Rights Reserved 2002

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4.

(c)

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(i)

Suggest why borazine reacts with HCl while benzene does not.

(ii)

Borazine reacts with HCl to give an addition product with molecular formula B3N3H9Cl3 . Draw the structure of a molecule of B3N3H9Cl3 .

(2 marks) (d)

Draw the three-dimensional structure of hexagonal boron nitride, indicating clearly the B−N distance within a layer and the distance between two layers. Label, on your diagram, the types of interactions present in the compound.

(3 marks) (e)

Suggest why hexagonal boron nitride is a poor conductor of electricity.

(1 mark)

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5.

(a)

Two acylic structural isomeric compounds have the molecular formula C3H6O3. Both are optically active and have infrared absorptions at 3400 cm–1 and 1700 cm–1. Neither possesses an alkoxy group. (i)

Draw the structure of each of the compounds. Label one of these structures ‘A’ and the other ‘B’.

(ii)

Suggest a chemical test, giving the expected observation, to distinguish between the compounds represented by ‘A’ and ‘B’.

(iii)

Give the structure of the major organic product formed when the two compounds are treated separately with excess LiAlH4. product from the compound represented by ‘A’

product from the compound represented by ‘B’

(6 marks)

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5.

(b)

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Suggest reagent(s) to accomplish each of the following single-step transformations: O (i)

OH

O

CH3C(CH2)4COCH3

O

CH3CH(CH2)4COCH3

NO2

NH2

(ii) (CH2)2CH=CH2

CHO

(CH2)2CH=CH2

CO2H

(iii) COCH3 OH

COCH3 OH

(3 marks)

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6.

(a)

Outline a synthetic route, in not more than four steps, to accomplish each of the following transformations. In each step, give the reagent(s), conditions and the structure of the organic product. O

CH2NH2

(i)

NH2

(ii)

NH2

(6 marks) 2002-AL-CHEM 1–12 保留版權 All Rights Reserved 2002

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6.

(b)

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Under suitable conditions, sucrose undergoes hydrolysis to give glucose and fructose. CH2OH

CH2OH

O

O

OH O

OH OH

OH

HO CH2OH

sucrose (i)

Draw a ring structure for glucose and one for fructose. glucose

(ii)

fructose

When treated with Fehling’s reagent, sucrose and glucose demonstrate different behaviour. (I)

What are the major chemical components of Fehling’s reagent ?

(II)

Explain why sucrose and glucose demonstrate different behaviour when treated with Fehling’s reagent.

(5 marks) END OF SECTION A 2002-AL-CHEM 1–13 保留版權 All Rights Reserved 2002

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SECTION B Answer ALL questions in this Section. Write your answers in the spaces provided. 7.

(a)

An experiment was carried out to determine the percentage by mass of tin in a sample of bronze, an alloy of copper and tin : 15.03 g of the finely divided sample was warmed with excess 1 M sulphuric(VI) acid to convert all the tin to tin(II) sulphate(VI). The mixture was filtered to remove copper which did not undergo reaction. The colourless filtrate was then diluted to 250.0 cm3 with deionized water. Four portions of the diluted tin(II) sulphate(VI) solution, each of volume 25.00 cm3, were titrated against 0.0205 M potassium manganate(VII) solution. The titres were 23.90 cm3, 23.35 cm3, 23.40 cm3 and 23.35 cm3. The equation for the reaction involved in the titration is as follows: 5Sn2+(aq) + 2MnO4– (aq) + 16H+(aq) → 5Sn4+(aq) + 2Mn2+(aq) + 8H2O(l) (i)

Describe how the end point of the titration can be detected.

(ii)

Calculate the percentage by mass of tin in the sample of bronze.

(5 marks) 2002-AL-CHEM 1–14 保留版權 All Rights Reserved 2002

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7.

(b)

Devise an experiment, using chemicals and apparatus commonly available in a school laboratory, to show that the reaction of peroxodisulphate(VI) ions with iodide ions can be catalysed by iron(III) ions. S2O82– (aq) + 2I– (aq) → 2SO42– (aq) + I2(aq)

(5 marks)

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8.

(a)

In an attempt to prepare 1-methylcyclopentene, 1-methylcyclopentanol was allowed to react with phosphoric(V) acid. The reaction mixture was then subjected to simple distillation. (i)

Draw a labelled diagram to show the set-up of apparatus used in a simple distillation.

(ii)

Suggest a chemical test, giving the expected observation, to show the presence of an alkene in the distillate.

(iii)

The distillate was known to contain a small amount of unreacted 1-methylcyclopentanol. Suggest a method to separate it from the desirable product.

(iv)

Is 1-methylcyclopentene the only compound obtained after the suggested separation method in (iii) ? Explain.

(6 marks) 2002-AL-CHEM 1–16 保留版權 All Rights Reserved 2002

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8.

(b)

A drug trafficker tried to isolate heroin from an illicit heroin block, which was in the form of heroin hydrochloride salt. H N

CH3 Cl

H O H3C C O

O

N

O

CH3 H

O C CH3

O

O H3C

C O

O

O C

CH3

heroin

heroin hydrochloride salt

The drug trafficker ground the heroin block into powder and heated the powder with excess sodium hydroxide solution. Dichloromethane was then used to extract the organic product from the reaction mixture. After evaporation of dichloromethane, a white solid D, with a melting point significantly different from that of heroin, was obtained. (i)

Draw the structure of D. Suggest why D instead of heroin was obtained.

(ii)

Suggest a workable method to obtain heroin from heroin hydrochloride.

(iii)

Suggest a reagent to convert D to heroin.

(4 marks)

END OF SECTION B 2002-AL-CHEM 1–17 保留版權 All Rights Reserved 2002

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SECTION C

Answer ONE question only and write your answers in the AL(D) Answer Book. Marks will be allocated approximately as follows : chemical knowledge organization presentation (including use of language)

50% 30% 20%

Equations, suitable diagrams and examples are expected where appropriate. The examiners are looking for the ability to analyse, to evaluate and to express ideas.

Marks 9.

Write an essay on the chemistry of sulphuric(VI) acid. (20 marks)

10.

Write an essay on air pollution arising from coal-fired electricity generating plants and on measures to reduce the amount of air pollutants in the flue gas. (20 marks)

END OF PAPER

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Useful Constants Gas constant, R = 8.31 J K–1 mol–1 Faraday constant, F = 9.65 × 104 C mol–1 Avogadro constant, L = 6.02 × 1023 mol–1 Planck constant, h = 6.63 × 10–34 J s Speed of light in vacuum, c = 3.00 × 108 m s–1 Ionic product of water at 298 K, Kw = 1.00 × 10–14 mol2 dm–6 Specific heat capacity of water = 4.18 J g–1 K–1

Characteristic Infra-red Absorption Wavenumber Ranges (Stretching modes) Wavenumber range /cm–1

Bond

Compound type

C=C C=O C≡C C≡N O–H C–H O–H N–H

Alkenes Aldehydes, ketones, carboxylic acids, esters Alkynes Nitriles Acids (hydrogen-bonded) Alkanes, alkenes, arenes Alcohols, phenols (hydrogen-bonded) Amines

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1610 to 1680 1680 to 1750 2070 to 2250 2200 to 2280 2500 to 3300 2840 to 3095 3230 to 3670 3350 to 3500

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– 19 –

4 Be 9.0 12 Mg 24.3 20 Ca 40.1 38 Sr 87.6 56 Ba 137.3 88 Ra (226)

3 Li 6.9 11 Na 23.0 19 K 39.1 37 Rb 85.5 55 Cs 132.9 87 Fr (223)

**

*

II

I

GROUP 族

58 Ce 140.1 90 Th 232.0

21 Sc 45.0 39 Y 88.9 57 * La 138.9 89 ** Ac (227)

59 Pr 140.9 91 Pa (231)

22 Ti 47.9 40 Zr 91.2 72 Hf 178.5 104 Rf (261)

60 Nd 144.2 92 U 238.0

23 V 50.9 41 Nb 92.9 73 Ta 180.9 105 Db (262)

H 1.0

1

61 Pm (145) 93 Np (237)

24 Cr 52.0 42 Mo 95.9 74 W 183.9

62 Sm 150.4 94 Pu (244)

25 Mn 54.9 43 Tc (98) 75 Re 186.2

63 Eu 152.0 95 Am (243)

26 Fe 55.8 44 Ru 101.1 76 Os 190.2

64 Gd 157.3 96 Cm (247)

27 Co 58.9 45 Rh 102.9 77 Ir 192.2

65 Tb 158.9 97 Bk (247)

28 Ni 58.7 46 Pd 106.4 78 Pt 195.1

relative atomic mass 相對原子質量

atomic number 原子序

PERIODIC TABLE

66 Dy 162.5 98 Cf (251)

29 Cu 63.5 47 Ag 107.9 79 Au 197.0

週期表

67 Ho 164.9 99 Es (252)

30 Zn 65.4 48 Cd 112.4 80 Hg 200.6

68 Er 167.3 100 Fm (257)

III 5 B 10.8 13 Al 27.0 31 Ga 69.7 49 In 114.8 81 Tl 204.4

69 Tm 168.9 101 Md (258)

IV 6 C 12.0 14 Si 28.1 32 Ge 72.6 50 Sn 118.7 82 Pb 207.2

70 Yb 173.0 102 No (259)

V 7 N 14.0 15 P 31.0 33 As 74.9 51 Sb 121.8 83 Bi 209.0

71 Lu 175.0 103 Lr (260)

VI 8 O 16.0 16 S 32.1 34 Se 79.0 52 Te 127.6 84 Po (209)

VII 9 F 19.0 17 Cl 35.5 35 Br 79.9 53 I 126.9 85 At (210)

0 2 He 4.0 10 Ne 20.2 18 Ar 40.0 36 Kr 83.8 54 Xe 131.3 86 Rn (222)

2002 A-Level Chemistry Paper 1 Section A 1.

2.

(i)

7.94 × 10–7 mol dm–3

(ii)

20

(a)

(i)

444 kPa

(b)

(ii)

3.8 × 10–3 dm3 mol–1 s–1

(a)

Section B 7.

(ii)

9.46

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