P2 Quest

8/3/2019 P2 Quest

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SEKOLAH MENENGAH KEBANGSAAN SEAFIELD, SUBANG JAYA

Name : …………………………………………..

Form: 6 ………

Upper Six Time: 2 ½ hours

Trial Examination

2009

CHEMISTRY

Paper 2

Section A [40 marks] Answer all the questions in this section.

Instructions to candidates:

Answer all the questions in Section A. Write your answers

in the spaces provided.

Answer any four questions from Section B. For this

section, write your answers on the answer sheets provided. Begin each answer on a fresh sheet of paper and arrange your

answers in numerical order. Tie your answer sheets to this

booklet.

All working should be shown. For numerical answers, units should be quoted wherever they are appropriate

Answers may be written in either English or BahasaMalaysia.

A Data Booklet is provided .

For examiner’s use

1

2

3

4

5

6

7

8

9

10

Total

Prepared by:

………………………..

(Pn. Looi Chui Yean)

Checked by:

…………………………

(Pn. Poh Bee Lee)

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

Approved by:

……………………..

(Pn. Loy Joke Jong)

8/3/2019 P2 Quest


Section A [40 marks]

Answer all the questions in this section.

1. An organic acid has the following composition by mass: C, 40.0%; H, 6.7%; O, 53.3%. Its mass

spectrum shows major peaks (including the molecular ion) at the following m/e values:

15, 43, 45, and 60.

(a) Calculate the empirical formula of the acid, and use the mass spectrum to suggest its molecular

formula.

[3 marks]

(b) From the molecular formula, identify the species responsible for the peak with m/e value 43.

[1 mark]

(c) When measurements are made of the relative molecular mass, in an organic solvent like pentane,

a value of 120 is obtained. Suggest an explanation for this, and draw the structural formula of

the species formed.

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….

[3 marks]

(d) When 1.00 g of the pure acid is dissolved in water and made up to 100 cm3, the resulting pH is

2.55. Calculate the hydrogen ion concentration in this solution and the K a of the acid.

2

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[3 marks]

2. (a) (i) Write the electronic configuration of the aluminium ion.

…………………………………………………………………………………………………….

[1 mark]

(ii) State the block in the Periodic Table to which aluminium belongs.

…………………………………………………………………………………………………….

[1 mark]

(b) The electrical conductivity of a metal can be explained by the band theory.

(i) Sketch diagrams showing the conduction band and valence band of a metal and a

semiconductor.

Conduction band and valence band of a metal

Conduction band and valence band of a semiconductor

[2 marks]

(ii) Is the conductivity of a semiconductor affected by an increase in temperature? Explain.

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….

[2 marks]

(c) When aluminium chloride reacts with chloride ions, as shown by the equation below, a

coordinate bond is formed.

AlCl3 + Cl− → AlCl4−

(i) What is a coordinate bond?

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….

[1 mark]

(ii) What is the hybridization of the aluminium atom in AlCl3 and AlCl4− ?

AlCl3 …………………………………….

AlCl4− …………………………………….

[2 marks]

(iii) What is the shape of the AlCl4− ion?

…………………………………………………………………………………………………….

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[1 mark]

3. In an experiment on electrolysis, two cells are connected in series as shown below. Cell I consists of

two copper electrodes immersed in an aqueous solution of copper(II) sulphate. Cell II consists of

carbon electrodes immersed in concentrated sodium chloride solution.

(a) Write ionic equations for the reactions at electrodes A, B, C and D

Electrode Ionic equation

A

B

C

D

[4 marks]

(b) If a current of 2.5 A is passed through the circuit for 30 minutes, determine the change of mass of

electrode A.

[3 marks]

(c) (i) Explain what happens to the concentration of copper (II) sulphate solution in cell I during

the electrolysis.

……………………………………………………………………………………………………………..

……………………………………………………………………………………………………………..

[2 marks]

(ii) Explain why copper metal is not suitable as electrode C

……………………………………………………………………………………………………………..

[1 mark]

4

Copper(II)sulphate

solution

Copper

Concentrated

sodium chloride solution

Cell I

A

Carbon

Cell II

A B C D

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4. (a) Starting from 1-bromopropane, CH3CH2CH2Br, show the reaction schemes to synthesize the

following carboxylic acids.

(i) CH3CH2COOH

……………………………………………………………………………………………………………..

……………………………………………………………………………………………………………..

[2 marks]

(ii) CH2CH2CH3COOH

……………………………………………………………………………………………………………..

……………………………………………………………………………………………………………..

[2 marks]

(b) Write equations for the reactions between benzoyl chloride, C6H5COCl, and the following

compounds and name the organic products according to the IUPAC nomenclature.

(i) CH3 NH2

……………………………………………………………………………………………………………..[2 marks]

(ii) C6H5OH

……………………………………………………………………………………………………………..

[2 marks]

(c) Aspirin has the following structure.

Write the formula of the products formed when aspirin is heated with potassium hydroxide

solution.

[2 marks]

5

C − OH

׀׀

O

O

׀׀O − C − CH

3

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Section B [60 marks]

Answer any four questions in this section.

5. (a) The chemical bonding in water molecules is a result of the overlapping of the orbitals of

oxygen and hydrogen atoms.

(i) What is meant by orbital?

(ii) Draw a labelled diagram showing the overlapping of orbitals in water molecules.

(iii) Explain why the bond angle in a water molecule is 104.5o as compared to 109.5o in

a methane molecule.

[8 marks]

(b) In each of the following compounds, state the intramolecular and intermolecular bonding. Draw the Lewis structures to show the intramolecular bonds in the molecules

(i) ammonia

(ii) hydrogen chloride

(iii) carbon dioxide

[7 marks]

6. The table below shows the initial concentrations of two compounds A and B, and also the initial rate of the reaction that takes place between them at constant temperature.

Experiment Initial concentration of A

/mol dm-3

Initial concentration of B

/mol dm-3

Initial rate

/ mol dm-3 s-1

1 0.20 0.20 3.5 x 10-4

2 0.40 0.40 1.4 x 10-3

3 0.80 0.40 5.6 x 10-3

(a) (i) Derive the rate equation for the reaction.

(ii) What are the units of the rate constant k?

(iii) Explain why rate equations cannot be written from the stoichiometric chemical equation for

the reaction, but must be

Rate = k[A]x [B]y

where x and y are the order of the reaction with respect to reactants A and B respectively.

[8 marks]

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(b) The curve below represents the Maxwell-Boltzmann distribution of molecular energies at

temperature T1 for the gases, hydrogen and iodine. Ea is the activation energy for the reaction.

(i) Draw a complete diagram to show the comparison of the molecular energies of the

mixture at temperature T2, a temperature lower than T1.

(ii) Explain the meaning of activation energy

(iii) The rate of reaction generally increases with an increase in temperature. State tworeasons.

(iv) What are the factor(s) that can affect the activation energy?

[7 marks]

7. (a) The key reaction during the Contact process for manufacturing sulphuric acid is as follows:

2SO2 (g) + O2 (g) 2SO3 (g) ∆ H = -197 kJ mol-1

When a 2:1 ratio of sulphur dioxide and oxygen gas at an initial total pressure of 3.0 atm is passed

over a catalyst at 430 oC, the partial pressure of sulphur trioxide at equilibrium is found to be 1.9

atm.

(i) Calculate the partial pressure of SO2 and O2 at equilibrium and hence the new total pressure .

(ii) Write an expression for the equilibrium constant, K p, and calculate its value.

[6 marks]

(b) In the laboratory preparation of 2-nitrophenol, 4-nitrophenol is also formed. 2-nitrophenol may be

separated from 4-nitrophenol by steam distillation. A sample of 2-nitrophenol is obtained by steam

distillation at a pressure of 101 kPa.

(i)State an advantage of steam distillation over fractional distillation.

(ii) Given that the vapour pressure of water at the temperature of the distillation is 95 kPa,

calculate the mass of 2-nitrophenol present in 100g of distillate

[Relative molecular mass, Mr of nitrophenol is 139]

[5 marks]

(d) The solubility of lead (II) chloride decreases when dilute hydrochloric acid is added but its

solubility increases on adding concentrated hydrochloric acid. With the aid of equations,

explain this observation.

[4 marks]

7

Molecular energyE

a

T1

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8. (a) (i) Carbon, silicon, germanium, tin and lead are elements in Group 14 of the Periodic Table.

Describe the variation in acid-base character of their oxides.

[4 marks]

(ii) Lead(IV) oxide is a dark-brown solid. When lead(IV) oxide is heated with an aqueoussolution of a manganese(II) salt in the presence of excess nitric(V) acid, the reaction that takes

place is as follows:

2Mn2+ + 4H+ + 5PbO2 → 2MnO4- + 5Pb2+ + 2H2O

Explain how lead(IV) oxide reacts, and state what is observed.

[4 marks]

(b) (i) Compare the thermal stability of CCl4 and SiCl4 and explain your answer.

[2 marks]

(ii) Explain the reactivity of CCl4 and SiCl4 with water. Write the chemical equations for the

reactions.

[5 marks]

9. (a) The formula of compounds R and S is given as follows.

CH3CH(OH)C3H7 CH3CH=CHC2H5

R S

(i) Draw the structural formulae for all the isomers which can be represented by themolecular formulae R and S.

(ii) Write an equation for the reaction between compound R and excess concentrated

sulphuric acid at 170 oC.

(iii) Write the equation and state the conditions to show how compound S can be

converted to an alkane.

[7 marks]

(b) Methylbenzene reacts with chlorine under two different sets of conditions to give

compound A or compound B.

(i) Describe the conditions used to produce A and B respectively.

(ii) Describe a reaction which you could distinguish between A and B. State the reagents and the

observations with each compound.[4 marks]

8

CH3

Cl

CH2Cl

A B

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(c) During aromatic substitution, the position of the incoming group, the new substituent, is

determined by the nature of the group already present in the ring. For example, the following

reactions produce bromo-compounds shown:

Use this knowledge to devise two-step syntheses, starting with methylbenzene, of the following

compounds:

(i) 4-nitrobenzoic acid

(ii) 3-nitrobenzoic acid

Identify the reagents at each step, and draw the structural formulae of the intermediates.

[4 marks]

10. (a) What is structural isomerism? Draw the structural formulae for all the isomers with the molecular

formula C4H9Br.

[5 marks]

(b) The chemical properties of three of the isomers in (a) are described below. Identify compounds

D, E and F and explain the reactions involved.

(i) Hydrolysis of D with aqueous solution of sodium hydroxide produces compound C4H10O.

The oxidation of C4H10O will form compound C4H8O. When C4H8O is heated with iodine

in an aqueous solution of sodium hydroxide, a yellow precipitate is formed.

[4 marks]

(ii) Hydrolysis of E produces a compound that is stable in acidified potassium

manganate(VII).

[3 marks]

(iii) The elimination of hydrogen bromide from F through reflux with a solution of sodium

hydroxide in ethanol produces a hydrocarbon C4H8. When C4H8 is heated in acidified

potassium manganate(VII), ethanoic acid is produced.

[3 marks]

9

CH3

bromination

CH3

Br

COOH

bromination

COOH

Br

P2 Quest

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