pahang 2008 stpm chem - p2 quest

8/8/2019 Pahang 2008 Stpm Chem - p2 Quest

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CONFIDENTIAL

Identity card number................ ........... Centre number/index number:....... ...... ..

(Nombor kad pengenalan) (Nombor pusat/angka giliran)

962/2

PEPERIKSAAN PERCUBAAN

SIJIL TINGGI PERSEKOLAHAN MALAYSIA

CHEMISTRY

PAPER 2

Two and a half hours

For examiners

use

1

2

3

4

5

6

7

8

9

10

Total

This question paper consists of 9 printed pages.

Instructions to candidates:

DO NOT OPEN THIS QUESTION PAPER UNTIL

YOU ARE TOLD TO DO SO.

Answerall questions in section A.Write your answers inthe spaces provided.All working should be shown.Fornumerical answers,units should be quoted whereverthey are appropriate.

Answer any four questions in section B.Write youranswers on the answer sheets provided.Begin eachanswer on a fresh sheet of paper and arrange youranswers in numerical order.Tie your answer sheets tothis question paper.


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Section A [ 40 marks ]

Answerallquestions in this section.

1. The lattice energies of lithium chloride and sodium chloride are 848 kJ mol1

and

776 kJ mol1 respectively.

( a ) Define the term lattice energy by using lithium chloride as an example. [2]

.......................................................................................................................................................

.......................................................................................................................................................

.......................................................................................................................................................

( b ) Explain why the lattice energy of lithium chloride is more exothermic than that of

sodium chloride. [2]

.......................................................................................................................................................

.......................................................................................................................................................

( c ) State the relationship between lattice energy, enthalpy change of hydration ( Hhyd)

and the enthalpy change of solution ( Hsoln ). [1]

.......................................................................................................................................................

( d ) The values of the enthalpy change of hydration ( Hhyd) for a few ions are given in

the following table .

Ion Enthalpy change of hydration ( Hhyd)/ kJ mol1

Li+ 499

Cl

381

( i ) Draw a Born-Haber cycle to determine the enthalpy change of solution

(Hsoln ) of lithium chloride. [2]

( ii ) Calculate the enthalpy change of solution ( Hsoln ) of lithium chloride. [2]

( iii ) How would you expect the temperature to change when lithium chloride is

dissolved in water? [1]

.......................................................................................................................................................


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2 The Haber process is used in the industrial production of ammonia. The reaction equationis as follows.

N2(g) + 3H2(g) 2NH3(g) H

= -92 kJ mol

(a) At a temperature of 500o C and a pressure of 500 atm, the system is in a state of

dynamic equilibrium. Explain what is meant by the term dynamic equilibrium. [2]

...............

...............

(b) (i) Name a catalyst for the Haber process.

.

(ii) Explain why the catalyst in (i) does not alter the equilibrium position in this

process. [2]

...

(c) Ammonia gas forms dense white fumes of ammonium chloride when reacted with

hydrogen chloride gas.

(i) Write an equation for the reaction

....................................................................................................................................

(ii) State the hybrid orbitals of the nitrogen atom in ammonia and ammonium

chloride.

Ammonia :

...

Ammonium chloride:

.. ............................

(iii) Explain why ammonia can act as a ligand in a complex ion.

...

(iv) State the contents of a tank of ammonia gas which is left to stand in a hot spotfor a few days. Give a reason for your answer.

...................

................[6]


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3. Some elements of the third period are as follows: Na, Mg, Al, Si, P, Cl, Ar.

(a) Which of the elements exist as diatomic molecules at room temperature and

pressure? [1]

.......................................................................................................................................

(b) Which element has the largest first ionisation energy? [1]

.......................................................................................................................................

(c) (i) Which of these elements form a simple covalent chloride that reacts with water

to give a white precipitate? [1]

...................................................................................................................................

(ii) Write an equation for the reaction in (c) (i). [1]

...................................................................................................................................

(d) (i) Name an element that forms an amphoteric oxide. [1]

............................................................................................................................

(ii) Write equations to show the amphoteric nature of the oxide in ( d ) ( i ) with

HCl(aq) : ................................................................................................ .......................

NaOH(aq): ..............................................................................................................

[2]

(e) Chlorine reacts with NaOH(aq) under different conditions to produce ClO and

ClO3 ions.

(i) State the conditions required to prepare ClO3

ion.

.................................................................................................................................

(ii) Write an equation for the preparation of the ClO3 ion.

.................................................................................................................................

(iii) State a use for sodium chlorate(V).

..................................................................................................................................[3]


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4.(a) Polymers can be classified as thermoset, thermoplastic and elastomer.

(i) What is meant by the term elastomer?

.................................................................................................................

........................................................................................................................................

(ii) Give an example of an elastomer and state a use for this elastomer.

Example:.......................................................................................................................................

Use : ............................................................................................................................................

[3]

(b) The structures of four isomers of the hydrocarbon C4H8 are shown below.

H H H H CH3 CH3C= CH2 C=C C=C C=CH2

CH3CH2 CH3 CH3 CH3 H CH3

P Q R S

(i) Which structures show geometrical isomerism?

.....................................................................................................................................

(ii) When P, Q, R and S are reacted with steam, a pair of optical isomers are

produced. Draw the structures of these isomers.

(iii) Draw the structure of the organic product formed when S is reacted with the

following reagents.

Cold KMnO4(aq) :

Hot acidified KMnO4(aq) :

HCl(g):[7]


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Section B [ 60 marks ]

Answer anyfour questions in this section.

5. ( a ) The preparation of coal gas involves the following reaction:

H2O( g ) + C( s ) H2( g ) + CO( g ) H= + 131 kJ mol1

( i ) State and explain the effect of an increase in pressure and temperature on the

position of equilibrium . [4]

( ii ) At 700C, the partial pressures of steam and hydrogen are 90 kPa and 183 kPa

respectively at equilibrium. Write an expression for the equilibrium constant,

Kp , in terms of partial pressure and give its units. Hence, calculate the value

ofKp. [4]

( b ) Ethanoic acid is a weak acid. It is used as a flavouring and a food additive in our diet.

( i ) Define the asid dissociation constant,Ka, of ethanoic acid. [1]

( ii ) Calculate the pH of a 1.0 dm3 solution containing a mixture of 0.40 mol dm3 of

ethanoic acid and 0.20 mol dm3 of sodium ethanoate solution.

[Ka, of ethanoic acid = 1.80 x 105 mol dm3 ] [3]

( iii ) Calculate the change in the pH value recorded when 0.050 mol of sodium

hydroxide is added to 1.0 dm3 of distilled water. [3]

6. ( a ) State Hess Law. [2]

( b ) ( i ) Define standard enthalpy of combustion for carbon monoxide and

write the equation for the reaction involved.

(ii) By using the data below, calculate the standard enthalpy of combustion

for carbon monoxide.

2 Fe (s) + 3/2 O2 (g) Fe2O3(s) H

= -822kJ

Fe2O3(s) + 3 CO (g) 2 Fe(s) + 3 CO2 (g) H

= -27kJ[6]

(iii) Based on the data below, explain why sodium metal reacts vigorously

and exothermically with chlorine gas.

Na(s) Na+ (g) H

= +604kJmol-1

Cl2 (g) Cl-(g) H

= -260kJmol

-1

[7]


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7. (a) What do you understand by the termcomplex ion ? [3]

(b) (i) Name and state the shape of [Cu(NH3)4 ]2+

?

(ii) Name the complex ion [Cr(NH3)4Cl2]2+

. This complex ion exhibit isomerism.

Identify the type of isomerism involved and draw its isomers.

[6]

(c) Transition metals or its compounds are widely used in heterogenous catalytic

activity.. Give a brief description of the use of a heterogeneous catalyst in the

Contact Process. [6]

8. (a) Aluminium is the most abundant metal on earth.It is commonly found as acomponent in the structure of silicate clays containing aluminium oxide layers.

Aluminium ions might be present within the silicate layers.

(i) Describe how the aluminium oxide layers is involved in the structure of

2:1 clay such as montmorillonite. [2]

(ii) Why is soil containing montmorillonite are not suitable for agriculture. [2]

(b) (i) Explain why an aqueous solution of aluminium salts is acidic. Write an

equation to show the reaction involved. [4]

(ii) Explain the effect of the charge density of Al3+ ions on bonding.

Describe why aluminium chloride sublimes. [7]

9. (a) The structural formula of 2-phenylmethyl-butan-2-ol is shown below.

(i) Identify two possible pairs of Grignard reagent and another respondent

chemical substance that can be used to prepare 2-phenylmethyl-butan-2-ol.

[4]

(ii) Write an equation for the reaction above. [1]


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(b) When chlorine gas is bubbled through methylbenzene, a compound Q is produced.

It can be prepared by using Grignard reagents.Compound Q has the molecular

formula, C7H7CI. It forms a white precipitate on warming with ethanolic silver

nitrate.

(i) Write all the structural formulae of isomers with the molecular formula

C7H7C1. [4]

(ii) Which of the compounds in b(i) is produced in the above reaction?State the conditions for the reaction. [2]

(iii) Write the chemical equation for the reaction between Q and ethanolic silver

nitrate. [2]

(iv) Explain why ethanolic silver nitrate and not aqueous silver nitrate is used for

the reaction. [2]

10. (a) An organic compound P with relative molecular mass of 126.5 has the following

composition by mass: carbon, 66.4%; chlorine, 28.1%; and hydrogen, 5.5%.

(i) Determine the molecular formula of P.

(ii) When P is refluxed with aqueous potassium hydroxide, Q is formed.

Controlled oxidation of Q producesR that gives an orange precipitate S

with 2,4-dinitrophenyhydrazine. Continued oxidation ofR produces T,

a white solid. Determine the structural formulae of P, Q, R, S and T.

[8]

(b) 2-bromo-2-methylpropane undergoes hydrolysis when boiled with aqueous

potassium hydroxide.

(i) Describe the mechanism of the hydrolysis.

(ii) State the effect of the concentration of aqueous potassium hydroxide on the

rate of hydrolysis.

[7]

pahang 2008 stpm chem - p2 quest

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