JABATAN PELAJARAN JOHOR

SIJIL TINGGI PERSEKOLAHAN MALAYSIA

Instructions to candidates:

Answer all the questions in Section A in (he spaces provided, All working must be shown. For numerical answers, unit must be quoted wherever they are appropriate.

Answer any four questions from section B. For this section, write your answers on the answer sheets. Begin each answer on afresh sheet of paper and arrange your answers in numerical order. Tie your answer sheets to this booklet.

Answers may be written in either English or Malay.

A Data Booklet is provided.

For Examiner's use (Untuk kegunaan

pemeriksa)

1 2

3

4

5 6

7

S

9

10 Total

(Jumlah)

This question paper consists of23 printed pages.

STPM 962/2 *This question paper is CONFIDENTIAL until the examination is over. CONFIDENTIAL*

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Section A [40 marks]

Answerall the questions in this section.

1. (a) A 20 dm3 closed vessel containing 1.5 mole H2gas, x mole N2 gas and 1.2 mole CO2

gas has a total pressure of 500 kPa at a temperature of 298 K.

(i) Calculatethevalueofx. [3marks]

(ii) 1.5 mole of neon gas was added into the 20 dm3 vessel. Calculate the

partial pressure of the hydrogen gas. [1 mark]

(b) Hydrazine, N2H4 is used as fuel for rocket.

(i) Write the electronic configuration of nitrogen atom. [1 mark]

(ii) Draw the dot ^ r o s s structure for hydrazine molecule. [1 mark]

(c) The boiling point of dimethyl ether(CH3OCH3) is lower than that of propanone

(CH3COCH3).

(i) Give a reason for the difference in their boiling points. [2 marks]

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(ii) State the types of hybridisation present in the carbon atoms of the two

compounds betow. [2 marks]

Dimethyl ether : ,

Propanone :

2 (a) (i) Give the definition for standard electrode potential. [2marks]

The standard reduction electrode potential for several half-cell reactions at 298 K are

shown in the table below.

Ha!f-ce!l reactions. Ee

S2Oaz' + 2 e ^ 2S042" +2.01

[Fe(CN)6]3- + e ^ [Fe(CN)6]4' +0.36

Fe35 ^ = T F ? 5 +0.77

~TZ + 2e ^ 2|- +0.54

When an aqueous solution of potassium peroxodisulphate , K2 S2O8 is added to an

aqueous solution ofpotassium iodide, K l , a reddish brown solution is obtained.

(ii) Write a balanced ionic equation for the above reaction. [2marks]

Write a cell diagram for the above reaction. [1 mark]

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(iv) Calculate the standard cell e.m.f., E0 Cfill for the reaction in (b)(iii). [1mark]

(b) The phase diagram of a substance W is shown below.

(i) State all the changes of phases of substance W at the following points as the

temperature increases. [2marks]

P: Q:

R: S:

T:

(ii) Base on the curve OY1 compare the density of solid W and liquid W. [1 mark]

(iii) Describe the change in melting point when pressure Is increased [1mark]

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3 A student examined the water from a mining pool which contains fead(ll) ions. The presence of Iead ions can be shown by the precipitation of yellow Iead (II) iodide. The solubility of a saturated solution of Iead(II) iodide at 15°C is 0.46 gdm"3.

(a) (i) Write an expression for the solubility product, Ksp, for Iead (II) iodide at 15 0C. [1 mark]

(ii) Calculate the concentration of Iead (II) ions in moldm"3. [2marks]

(iii) Calculate the concentration of iodide ions in moldm"3. [2marks]

(iv) Calculate the solubility product, Kspt for Iead (Il) iodide. 11 mark]

(b) Strips of copper are dropped into a conical flask containing hot 50% nitric acid solution.

A colourless and very reactive gas is given off. The gas then reacts with oxygen in the air

to form a brown gas.

(i) Name the colourless gas . [1 mark]

(ii) Write the equation for the reaction between copper and nitric acid. [1 mark]

(iii) Identify the brown gas and write an equation for its formation [2marks]

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4. Pethidine is a powerful painkilling drug:

CO2CH2CH3 CO2CH2CH3

Pethidine E

(a) The pethidine molecule contains two functional groups, one which reacts with dilute

hydrochloric acid to give compound E.

{i) What type of reaction is this and what type of functional group does it show the

pethidine molecule to have? [2marks]

Name the other functional group in the molecule. State the type of reaction

undergone, and give the structural formula of each of the products, when

pethidine reacts under reflux with aqueous sodium hydroxide.

[3marks]

Functional group:

Type of reaction:

Structural formula:

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{b) 2-bromobutane reacts with aqueous hydroxide ions to give butan-2-ol.

(i) State the condition for this reaction. [1 mark]

(ii) State what type of mechanism is involved in this reaction. [1 mark]

(iii) State the reagents needed to convert 2-bromobutane to

CH3CH2CH(CH3)CH(OH)CH3 in two steps. [2 marks]

Step 1 :

Step 2 :

(iv) Name one reagent that can be used to differentiate between 2-bromobutane

and CH3CH2CH(CH3)CH(OH)CH3 without heating. [1 mark]

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Section B [60 marks]

Answerfour questions in this section,

5. (a) The major buffer system that is used to controi the pH of blood consists of carbonic

acid, H2CO3 and sodium hydrogen carbonate, NaHCO3, Explain how the system works in

controlling the pH ofthe blood, [4 marks]

(b) 20.0 cm3 of 0,20 mol dm'3 aqueous NH3 was titrated with 0.16 mol dm'3 aqueous

HCL Sketch a graph of pH against volume of HCl(aq) added during the titration process.

Mark and explain the position of the equivalence point. [4 marks]

(c) The activation energy, Ea, of a reaction can be calculated from the Arrhenius

equation: _ E / R T k = Ae "

where k = rate constant, R = gas constant, T = temperature, and A = frequency factor.

Rate constants for the decomposition of acetonedicarboxylic acid are k = 4.75 x 10^ s"1 at

293 K and k = 1,63 x 10'3's'1 at 303 K.

CO(CH2COOH)2 (aq) » CO(CH3)2(aq) + 2 C02(g)

(i) Calculate the activation energy, Ea , of this reaction. [4 marks]

(ii) Write the rate equation for the reaction. [1 mark]

(iii) What is the time taken for the concentration of CO(CH2COOH)2 (aq)

to change from 2,00 mol dm"3 to 1.00 mol dm*3 at 303 K. [2 marks]

6. (a) The following data are found of chlorine.

Enthalpy change of atomisation, AH1 = +121 kJ mor1

Electron affinity, AH2 = - 364 kJ mol'1

Enthalpy change of hydration, AH3 = - 381 kJ mol"1

By drawing an energy cycle, calculate the enthalpy change for the reaction, AH4.

V* CI2(Q) + water + e' > CP (aq) AH<.

Deduce the strength of chlorine as an oxidising agent based on the AH4 value obtained. [6 marks]

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(b) (i) Gases can only be tiquefled by pressure alone if their temperature is below their

'critical temperature', Tc. Above the critical temperature no amount of pressure will liquefy a

gas. Use the following data and suggest an explanation for their critical temperatures.

Gas formula Mr TcZ0C Methane CH^ ~~ t6 -82

Ammonia NH3 17 133

steam H2O 18 374

[5 marks)

(ii) In the industrial liquefaction of air, high pressure air is allowed to expand into a

region of Iow pressure, whereupon its temperature drops by a (arge amount. An ideal gas

does not show this behaviour. Give an explanation for the above observation. [4 marks]

7 The formation of magnesium oxide can be represented with a Born-Haber cycle as shown below.

Mg**(g) + O1Ig)

AH 7

V MgO(s)

(a) (i) Name the enthalpy change AH1, AH2 and AH7 [3marks]

| Affj

Mr(g)

| Aff1

Mg(g)

| Affl

Mg(s)

T

| Aff6;

018)

t bH.

0 ( g )

4 AH,

T c y g l

Atf,

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(b) (i) Gases can only be liquefied by pressure alone if their temperature is below their

'critical temperature', Tc. Above the critical temperature no amount of pressure will liquefy a

gas.

Use the following data and suggest an explanation for their critical temperatures.

Gas formula Mf TcZ0C Methane ChL 16 -82

Ammonia NH3 17 133

steam H2O 18 374

[5 marks]

(ii) In the industrial liquefaction of air, high pressure air is allowed to expand into a

region of Iow pressure, whereupon its temperature drops by a large amount. An ideal gas

does not show this behaviour. Give an explanation for the above observation.

[4 marks]

7 The formation of magnesium oxide can be represented with a Born-Haber cycle as shown below.

Mg '̂(g) + 0*-(g)

AH3

Mr(g)

A AH1

Mg(g) A

AW1

Mg(s)

I

| ^ o-(g)

| W,

0(g)

I WA

j o j ( g )

AH.

AH

MgO(s)

(a) (i) Name the enthalpy change AH i l AH2 and AH7 [3marks]

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(ii) From the following data,calcuiate the enthalpy change of formation , AHf, for magnesium oxide.

AH1

AH2

AH3

AH4 +AH5 + AH6

AH7

- +150 kJ mo!'1

= +736 kJ mol"1

= +1450 kJ mol"1

= +950 kJ mol"1

= - 3889 kJ mol'1 [3marks]

(iii)The lattice energy for barium oxide is -3152 kJ mol"1, while for magnesium oxide

is - 3889 kJ mol"\Explain this different in lattice energy. [3marks]

(b) Chlorofluorocarbons, CFCs, are small alkane molecules in which some ofthe

hydrogen atoms have been replaced by atoms of chlorine and fluorine.

(i) CFCs present an environment concern. Explain why and write equations for the

reactions involved. [4 marks]

(ii) A typical CFC is CCI2F2. Suggest a similar molecule which is more environment

friendly.Give your reasoning. [2 marks]

8 (a) (i) Explain why the smell of chlorine disappears when it is passed into cold and hot aqueous sodium hydroxide respectively. [5marks]

(ii) The boiling point of HF,HCI, HBr and Hl are shown below.

Hydrogen halide HF HCI HBr Hl

Boiling point(K) 293 188 206 ~ 238

Explainthe trend. [4marks]

(b) X is a complex compound with the molecular formula CrCI3. 6H20. An aqueous solution

of X containing 0.05 mol of solute will react completely with 0.05 mol of silver nitrate.

(i) Give the formula of complex X and state the type of isomerism is shown,

[2 marks]

(ii) Draw and name all isomers ofX. [4 marks]

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9. (a) Explain the term optical isomerism, using the compound CH3CH(OH)CH2CH3 as an

example. I 3 m a r k s J

(b) X1 C8H10O , liberates white fumes with phosphorous^) chloride. X reacts with alkaline

iodine to give yel!ow precipitates. When X is heated with an excess of concentrated

sulphuric acid, compound Y is formed, Y can be converted to X. Under suitable conditions ,

Y undergoes polymerization. Determine the structure of X and Y. Explain how you derive the structures and write the

Equations of the reactions involved. [7marks]

(c) Compounds A and B are two isomers with molecular formula CeH10O. A dissolves in

aqueous sodium hydroxide but B does not. B gives off white fumes with thionyl chloride and

forms a yellow precipitate with alkaline aqueous iodine but A does not. B is synthesised

starting from bromobenzene whereas A is from 4-ethylaniline.

Explain the above observations and write the structural formulae of A and B. [5 marks]

10. (a) Compounds R and S have the following structure.

^ C H 2 C H 2 N H 2 < ^QyCH 2 CONH 2

R S

(!) Write equations for the reactions, if any, when R and S react separately with

dilute hydrochloric acid under suitable conditions. [2 marks]

(ii) Describe briefly a chemical test, stating the reagents and conditions used, ar>d

observations, to distinguish between R and S. [3 marks]

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(b) State the reagents and conditions for steps I , Il and III. Draw the structural formulae of

A and B.

CH3CH2CH2Br — ^ A — ^ CH3CH2CH2CO2H

III

B * -< C ^ O H

CH3CH2CH3CO2CI

[5marks]

(c) Describe the scheme of reactions(in not more than 3 steps), stating the reagents and

conditions, forthe synthesis of < ^ Q ^ C O O C 2 H 6 starting f r 0 m < ^ Q ^ C H 3 •

[5 marks]

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