1

ST ANDREWS JUNIOR COLLEGE

JC1 Final Examination

Chemistry

Higher 2

9647

4 Oct 2010

2 hours

Candidates answer on separate paper.

Additional Materials: Multiple choice answer sheet, Writing paper, Data Booklet

READ THESE INSTRUCTIONS FIRST

Write your name and civics group on all the work you hand in.

Write in dark blue or black pen.

You may use a soft pencil for any diagrams, graphs or rough working.

Do not use staples, paper clips, highlighters, glue or correction fluid.

Section A & B [20 marks]:

Answer multiple choice questions in Sections A and B on the answer sheet provided. This

answer sheet will be collected at the end of the first 30 minutes.

Section C [60 marks]:

Answer all 3 questions on the writing paper provided.

You are reminded of the need for good English and clear presentation in your answers.

The number of marks is given in brackets [ ] at the end of each question or part question.

This document consists of 19 printed pages including this page.

2

Section A

For each section there are four possible answers, A, B, C, and D. Choose the one you consider to

be correct.

1 The relative abundances of the isotopes of a sample of platinum are shown in the table

below.

Relative Isotopic Mass 194 195 196 197

Relative Abundance 32.3 33.2 26.8 7.7

What is the relative atomic mass of platinum in this sample?

A 194.9 B 195.0 C 195.1 D 195.5

2 In an experiment, 20 cm3 of a 0.500 mol dm-3 iodate IOx solution was run into an acidified

solution containing an excess of potassium iodide. Both the iodate and iodide ions reacted

to form iodine according to the following reaction:

IOx (aq) + (2x 1)I (aq) + 2xH+ (aq) xI2 (aq) + xH2O (l)

On titration, the liberated iodine was found to require 0.08 moles of sodium thiosulfate for

complete reaction, forming tetrathionate, S4O62, and iodide ions.

What is the value of x?

A 2 B 3 C 4 D 8

3 Gaseous particle S has a proton number of m and a charge of +1. Gaseous particle T has a

proton number of (m 2), the same number of nucleons as S, and is isoelectronic with S.

Which of the following statements correctly describes S and T?

A S has more neutrons than T.

B S requires less energy than T when another electron is removed from each particle.

C T has a larger ionic radius than S.

D T has a charge of 2.

3

4 Which graph correctly describes the behaviour of a fixed mass of an ideal gas?

A

B

C

D

5 Given the following data, predict the type of bonding and structure present in X, Y, and Z.

Compound

Melting

Point/ K

Electrical Conductivity

in solid state

Electrical Conductivity in

molten state

X 3820 Does not conduct Does not conduct

Y 273 Does not conduct Does not conduct

Z 1074 Does not conduct Conducts well

X Y Z

A giant covalent simple covalent metallic

B simple covalent giant covalent ionic lattice

C giant covalent simple covalent ionic lattice

D ionic lattice simple covalent metallic

P

Density 0

Constant T V

T/ 0C 0

Constant P

P

T/ 0C 0

Constant V PV

V 0

Constant T

4

6 The reaction pathway diagram below represents the reaction occurring with and without a

catalyst.

Which of the following statements is correct?

A E4 is the activation energy for the reverse catalysed reaction.

B The enthalpy change of the reaction is reduced using a catalyst.

C The enthalpy change of the forward reaction is (E2 E3).

D Reaction 1 is exothermic.

7 The following equation represents the rate determining step of a reaction conducted in an

experiment.

CH3Br + OH- CH3OH + Br

-

A large excess of OH- was used, resulting in a pseudo-first order reaction. The initial rate of

this reaction was found to be 5.78 x 10-3 mol dm-3 min-1. Given that the half life of the

reaction is 24 min, what is the initial concentration of CH3Br?

A 0.200 mol dm-3

B 0.138 mol dm-3

C 0.000240 mol dm-3

D Cannot be determined from the given information

Energy

Progress of reaction

E1

E2 E3

E4

reactants

products

Reaction 2

Reaction 1

5

8 Which of the following shows the correct order of lattice energies, placing the one with the

lowest numerical value first?

A BaCl2 < SrCl2 < MgCl2

B MgF2 < MgCl2 < MgBr2

C NaCl < MgCl2 < AlCl3

D BaCl2 < MgCl2 < SrCl2

9 Which of the following structural isomers of C8H16 exhibits both geometrical and optical

isomerism?

A CH2=CHCH2CH2CH2CH2CH2CH3

B (CH3)2C=CHCH(CH3)CH2CH3

C CH3CH=CHCH2CH2CH2CH2CH3

D CH3CH=CHCH2CH(CH3)CH2CH3

10 Which of the following is not the propagation step in the reaction between ethane and

chlorine under uv light?

A Cl + CH3CH3 CH3CH2 + HCl

B H + Cl2 Cl + HCl

C CH3CH2Cl + Cl CH3CHCl + HCl

D CH3CH2 + Cl2 CH3CH2Cl + Cl

6

11 Compound P has the following structure

Compound P

After compound P has reacted with hydrogen gas in the presence of nickel catalyst, how

many optical isomers will the product have?

A 25 B 26 C 27 D 28

12 Alkene Q, after reacting with hot acidified KMnO4, yields the following 3 carbon-containing

products.

CO2

Product 1 Product 2 Product 3

What could be the structure of compound Q?

A CH2=CHCH2CH2CH2CH2CH=CH2

B CH3C(CH3)=CHCH2CH2CH=CH2

C CH3C(CH3)=C(CH3)CH2CH=CH2

D CH3C(CH3)=CHCH=C(CH3)2

7

13 Lanosterol is a tetracyclic triterpenold which is the compound from which steroids are

derived. It has the following structure:

Which of the following statements about Lanosterol is true?

A Lanosterol is unable to decolourise liquid bromine.

B When Lanosterol is treated with cold dilute KMnO4, it would result in a product with 5

OH groups

C When Lanosterol reacts with hot acidified KMnO4, it would result in 3 products.

D Lanosterol is unable to rotate the plane of polarised light.

14 Which of the following properties of benzene is not directly attributed to the stability

associated with its delocalised electrons?

A It would undergo electrophilic reactions.

B It would undergo substitution rather than addition reactions.

C

The enthalpy change of hydrogenation of benzene is less than 3 times that of

cyclohexene.

D Benzene is less reactive than alkenes.

8

15 3-nitrobenzoic acid can be synthesised from a 2-step reaction of methylbenzene.

Methylbenzene 3-nitrobenzoic acid

Which of the following sequences of this synthesis is correct?

Step 1

Reagents and

conditions Step 2

Reagents and

Conditions

A Nitration Aqueous HNO3 and

Aqueous H2SO4,

reflux

Oxidation Hot acidified

K2Cr2O7

B Nitration Conc. HNO3 and

Conc. H2SO4, reflux

Oxidation Hot acidified

KMnO4

C Oxidation Hot acidified

K2Cr2O7

Nitration Aqueous HNO3 and

Aqueous H2SO4,

reflux

D Oxidation Hot acidified

KMnO4

Nitration Conc. HNO3 and

Conc. H2SO4, reflux

Step 1 Step 2 Intermediate

9

Section B

For each of the questions in this section, one or more of the three numbered statements 1 to 3 may

be correct. Decide whether each of the statements is or is not correct (you may find it helpful to put a

tick against the statements which you consider to be correct).

The responses A to D should be selected on the basis of

A B C D

1, 2, and 3 are correct 1 and 2 only are

correct

2 and 3 only are

correct 1 only is correct.

16 Which of the following solutions contain more ions than 20 cm3 of

1.0 mol dm-3 sodium phosphate, Na3PO4, solution?

1 20 cm3 of 1.4 mol dm-3 H2SO4 solution.

2 15 cm3 of 2.0 mol dm-3 MgCl2 solution.

3 40 cm3 of 1.0 mol dm-3 HNO3 solution.

17 In which of the following pairs is the bond angle in compound K greater than the bond angle

in compound L?

K L

1 H2Se H2O

2 NH3 XeF4

3 BH3 SF6

18 Given the reaction:

M (g) + N (g) O (g),

which of the following will cause a decrease in the rate constant?

1 Introducing an inhibitor

2 Decreasing the temperature of the reaction mixture

3 Decreasing the pressure of the system

10

19 Which of the following compounds could be formed by the reaction of propene with aqueous

bromine in the presence of sodium chloride?

1

2

3

20 Under what conditions will bromine react with the compound J below?

CC

CH

H

HH

H

Compound J

1 In the presence of AlBr3

2 Dissolved in water in the dark

3 In the presence of sunlight

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Section C

1 Phenol was used as the first surgical antiseptic in 1865. However, due to its carcinogenic

properties, safer antiseptics such as Trichlorophenol (TCP) has been synthesised which

retains its germicide properties without the toxicity of phenol.

One of the steps in the production of phenol involves the Friedel Crafts electrophilic

substitution of benzene using an acid catalyst to form cumene as shown in the following

reaction:

(a) The enthalpy changes of benzene, propene and cumene are given below.

H = +815 kJ mol-1

H = +623 kJ mol-1

H = +217 kJ mol-1

H = +125 kJ mol-1

By using the above data, draw an appropriate energy cycle to calculate the standard

enthalpy change of vapourisation of cumene. [3]

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1(b)

(i) Suggest a chemical test to distinguish between benzene and cumene. State the

reagents, conditions and the observations with each compound. [2]

(ii) When cumene is nitrated by a mixture of concentrated nitric acid and concentrated

sulfuric acid, the product consists largely of two isomers. Draw the structural

formulae of the two isomers. [2]

(iii) State the type of reaction in b(ii) and outline a mechanism for the above reaction. [3]

(c) Cumene can be oxidised to a hydroperoxide by passing air through multiple reactors

containing an aqueous emulsion of cumene at a pH within the range 8.5 to 10.5 as shown

in the following reaction:

With reference to the hydroperoxide molecule, state the C-Cx-O bond angle and the

hybridised state about Cx atom.

[2]

x

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1(d) (i) The hydroperoxide molecule is used as a drug to study the metabolism rate of liver

cells in rats. In a study carried out to determine the rate of removal of the

hydroperoxide from the rat cells, the reaction was found to have a constant half life

of 2.7 hours. Sketch a graph to show how the concentration of hydroperoxide

changes with time, assuming the initial concentration of hydroperoxide is

0.05 mol dm-3

[2]

(ii) What would be the qualitative effect on the rate constant by changing the

concentration of the hydroperoxide molecule? [1]

(e)

Phenol TCP sodium trichlorophenoxide

State and explain the order of increasing boiling points of phenol, TCP and sodium

trichlorophenoxide. [3]

(f) When 0.95 g of TCP is completely vapourised in a gas syringe at 300 C and

101 kPa, 220 cm3 of gaseous TCP is produced. Calculate the relative molecular

mass of the gas produced and suggest why there is a difference between the

theoretical value and the value calculated. [2]

[Total: 20 marks]

14

2 Ethane-1,2-diamine is used in large quantities for the production of many industrial chemicals

such as in pharmaceuticals and agrichemicals. Ethane-1,2-diamine is manufactured by reacting

ammonia and 1,2-dichloroethane as shown in the following equation:

(a) (i) Explain with the aid of a suitable diagram why boron trifluoride reacts with

ethane-1,2 -diamine in a molar ratio of 2:1.

(ii) State and outline the mechanism for the formation of 1,2-dichloroethane from a

suitable alkene of your choice.

(iii) Due to the bifunctional nature of ethane-1,2diamine, it readily forms heterocycles

such as imidazolidines as shown below. Predict, with the aid of a suitable diagram,

the solubility of imidazolidines in water.

[8]

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2(b) Ethane-1,2-diamine, (abbreviated as en), forms an ion of the molecular formula

IV2

22Pt en C

l .

To study the chemistry of this ion, a radioactive isotope of chlorine, *Cl was used.

The reaction between *Cl and IV2

22Pt en C

l can be represented by the following

equation:

II

IV IV

2

2Pt en2 2

22 2Pt en C C Pt en C C C

l l l l l

The rate of the above reaction is slow and can be increased in the presence of

II2

2Pt en

catalyst. The results of some investigation of the rate of this reaction are

shown below.

Experiment

IV2

22Pt en Cl

/ mol dm3

[*Cl-]

/ mol dm3

II2

2Pt en

/ mol dm3

initial rate

/ mol dm3 s1

1 0.80 0.10 0.20 0.409

2 0.40 0.05 0.10 0.049

3 0.40 0.05 0.20 0.102

4 0.20 0.05 0.10 0.025

(i) Determine the order of reaction with respect to each reactant and hence deduce the

rate equation.

(ii) Using data from Experiment 1, calculate a value for the rate constant, k, giving its

units.

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2(b) (iii) With the sketch of the Boltzmann distribution, explain how the use of a catalyst can

speed up the rate of a reaction. Also, state the effect of the catalyst on the rate

constant, k.

[6]

(c) An experiment is conducted to determine the standard enthalpy change of neutralisation

between ethane-1,2diamine, a diacidic base, and hydrochloric acid.

Aqueous ethane-1,2diamine is added to 45 cm3 of 1 mol dm-3 aqueous hydrochloric acid.

The changes in temperature are recorded and the following graph was obtained.

(i) Using the graph obtained, calculate the standard enthalpy change of neutralisation,

assuming that 4.2 J is required to raise the temperature of 1 cm3 of solution by 1 oC.

(ii) Given that S= -205 J mol-1 K-1, calculate G and hence predict its spontaneity at

298K.

(iii) Is the spontaneity of the above neutralisation process dependent on temperature?

[6]

[Total: 20 marks]

Temperature/oC

Volume of base added/cm3

30.9

25.6

25.00

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3(a) Hex-1-ene is a co-monomer used in the production of polyethene, which is widely used to

manufacture plastic shopping bags. Some reactions of hex-1-ene are shown below.

Compound A

(i) Name and describe the type of reaction mechanism that occurs in Step 2.

Use R-CH2CH3 to represent the alkane in Step 2 while R = CH3(CH2)3

(ii) State the reagents and conditions for Step 1.

(iii) Compound A can exist as a pair of stereoisomers. Draw structural formulae to represent

the isomers.

[4]

(b) Sulfuryl chloride is a very good source of Cl2 which reacts with hex-1-ene to form an

important industrial solvent.

(i) State the electronic configuration of chlorine, Cl.

(ii) Sketch the shape of the singlyoccupied orbital in an atom of Cl.

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3(b) (iii) With reference to the Data Booklet, briefly explain why the first ionisation energy of

sulfur is lower than that of chlorine but the second ionisation energy of sulfur is

similar than that of chlorine.

[5]

(c) Halogens undergoes disproportionation in hot metal hydroxides to form chlorates (VII) and

bromates (VII), which contain only the XO4- ion (X = Cl or Br) as well iodates (VII) which

contains the ions IO53-, IO6

5- and IO4- .

(i) Draw the dot and cross diagram for IO65- and hence state the shape of the ion.

(ii) Consider the following ions: IO53-, IO6

5- and IO4-

State the polarity of the electric plate which the above ions would be deflected to

and also the ion which gives the most deflection.

(iii) The purity of iodates (VII) can be determined by adding an acidified solution of

potassium iodide and titrating the iodine produced with aqueous sodium

thiosulfate.

In one such analysis, a sample of 0.200 g of sodium iodate (VII), Na5IO6, was

dissolved in water and treated with an excess of acidified KI to yield iodine and

water as the only products. The iodine liberated required 22.0 cm3 of

0.100 mol dm-3 sodium thiosulfate to reach the end-point.

a) Using half equations, write a balanced ionic equation for the reaction of

iodate (VII) with acidified iodide.

b) Hence, calculate the purity of the sodium iodate (VII) in the sample.

[7]

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3(d) Potassium iodate (VII), KIO4, is used as a source for iodine as an ingredient in baby

formula milk. Potassium iodate (VII) is also occasionally used as a maturing agent in

baking.

(i) The lattice energy of KIO4 is 1527 kJ mol-1 while the values of the enthalpy change of

hydration of the ions are listed below:

Ions Hhyd / kJ mol-1

K+ 1420

IO4- 295

Calculate the enthalpy change of solution of potassium iodate with the aid of an energy

level diagram.

(ii) By using your answer from (d)(i), and given the entropy change of solution of

potassium iodate (VII) is positive, predict whether potassium iodate is soluble in water

at room temperature and pressure. Give your reasoning,

[4]

[Total: 20 marks]