2003 cape chem unit 01 paper 01.PDF

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TEST

CODE 002671

FORM TP 23182

MAY/JUNE 2003

CARIBBEAN EXAMINATIONS COUNCIL

ADVANCED PROFICIENCY EXAMINATION

CHEMISTRY

UNIT 1 - PAPER 01

1 hour 45

m nut s

Candidates are advised to use the first 15 minutes for reading

through this paper carefully.

READ THE FOLLOWING INSTRUCTIONS CAREFULLY

1. This paper consists of NINE questions.

2. There are THREE questions from each Module. Answer ALL questions.

3. Write answers in this booklet.

4. ALL working must be shown in this booklet.

5. The use of non-programmable calculators is permitted.

6. AData Booklet is provided.

Copyright © 2002 Caribbean Examinations Council.

All rights reserved.

002671/CAPE/F 2003



2

MODULE I

Answer ALL questions.

2 U decays by a-emission to give an isotope of element X, which then decays

. Ina decay series, 29

by (3-emission to give element Y.

(a) Complete the equation for EACH of the decay processes described, by including the mass

and proton numbers for X and Y.

238

i) 92U

X a

Y+P

[ 2 marks]

(b) Complete the diagram in Figure1 to show how a - particles, (3- particles and y-rays would

be deflected by passage through an electric field, taking care to consider BOTH direction

and degree of deflection of EACH.

Figure 1

Particle

source

[ 4 marks]

GO ON TO THE NEXT PAGE



3

(c) The graph in Figure 2 represents a plot of number of neutrons on the vertical axis and the

number of protons for isotopes of the elements on the horizontal axis. Stable nuclei fall

within the ̀ band of stability' in which the n/p ratio ranges from 1 for light nuclei to 1.5 for

heavier nuclei. Radioactive decay leads to the formation of a more stable nucleus.

n/p ratio = 1

4

43 K

19

19 Proton number

Figure 2

Suggest the type of decay that would occur for 19 K based on its position as shown in

the diagram. Explain your reasoning.

[ 4 marks]

Total 10 marks


002671/CAPE/F 2003



2. (a) Name and describe the nature of the MAIN intermolecular forces between the following

molecules:

(i) NH3

(ii) CO2

[ 6 marks]

(b) Ammonia forms an addition compound with covalent beryllium chloride, BeCI2.

(i) Suggest the formula of the compound formed.

[ 1 mark ]

(ii) Draw a dot-cross diagram to show the electron distribution in the addition

compound.

[ 2 marks]




5

(iii) Draw a diagram to illustrate the shape of the addition compound.

[ 1mark]

Total 10 marks

3. (a) Explain the following terms:

(i) Bond energy

[ 2 marks]

(ii) Enthalpy change of combustion, AH

[ 2 marks]


00267 1 /CAPE/F 2003



6

(b) DMSO, dimethylsulphoxide, is an organic liquid having the molecular structure shown

below.

HOH

1 11 1

H C S C H

It is an excellent solvent and is known to penetrate the skin very readily. DMSO has the

potential for use as a drug in the treatment of arthritic pain.

Suggest ONE reason for the ability of DMSO to penetrate the skin.

[ 1 mark ]

(c) (i) Write an equation for the combustion of DMSO

[ 2 marks]


002671/CAPE/F 2003



7

(ii) Use the bond energy data in Table 1 to calculate AH of DMSO.

TABLE

I: BOND

ENERGY DATA

Bond

Energy / KJ mol-1

C - H

415

C S 27

S = 0

5 23

= 98

0-H

464

C=O

7

[ 2 marks

(d) Comment on the suitability of DMSO for use as a fuel.

[ 1 mark

Total 10 marks


002671 /CAPE/F 2003



MODULE 2

Answer ALL questions

4. Table 2 below shows the functional group analysis of the compounds, A, B, C and D.

TABLE 2

: FUNCTIONAL GROUPANALYSIS OF COMPOUNDS A - D

Compound

Test Observation

Structural Formula

of Functional Group

A

Br

in decolourisation

z

1,1,1, trichloro-

ethane

PCl

dense white

fumes

I

/ NaOH

yellow ppt.

C

litmus test blue -) red

PCl

dense white

fumes

D

litmus test

blue---) red

Br

(aq)

white ppt.

(a) Complete Table 2 by writing the structural formulae for EACH compound based on th

observations given [4mrk

002671/CAPE/F 2003

GO ON TO THE NEXT PAG



9

(b) Compound B is a fragrant liquid which when heated with excess concentrated H,,SO4

produces a gas, G, which decolourises bromine. When G reacts with HBr, two isomeric

compounds, E and F, with relative molecular mass of 123 are obtained.

Write the displayed formula for

EACH

of the following:

i) E

[ 1 mark]

[ 1 mark ]

[ 1 mark ]




r

10

(iv) G

[ 1 mark]

(v) -The

ionic intermediates formed in the production of:

a E

[ l mark ]

[ l mark]

Total 10 marks

002671/CAPE/F 2003




11

5. (a) State the type of reaction mechanisms involved in the following conversions:

i) C2H6

> CH3 CH7 Cl

ii) C3H7C1

> C H6

(iii) (CH3)3 CBr

(CH3)2 C(OH) CH3

[ 3 marks]

(b) State the conditions necessary for the conversions in

(i) (a) (i) above

ii) a) ii

) above.

[ 2 marks]

(c) Write the equations for the steps involved in the conversion shown in

(i) (a) (i) above

[ 3 marks]

ii) a) iii

) above.

[ 2 marks]

Total 10 marks


nn )ti71 Jr APRF 9003



12

6. (a) (i) Write the structural formulae of TWOproducts formed when methylbenzene i

treated with a mixture of concentrated nitric acid and concentrated sulphuric acid

[ 2 marks

(ii) Write

the equations showing the steps involved in the formation

of ONE of th

products identified in a) i).

[ 2 mark

(b) Give an explanation for EACH of the following:

(i) Methylbenzene is more susceptible to electrophilic attack than benzene.

[ 1 mark

(ii) The 2-position on the methylbenzene ring is attacked by electrophiles more readil

than the 3-position.

[ 1 mark

GO ON TO THE NEXT PAG

-



13

(c) For EACH

of the following pairs of compounds

, state ONE

simple chemical test that can

be used to distinguish between them.

(i) Ethanol and phenol

[ 1 mark ]

O

(ii) Phenol

(6 and ethanoic acid CH3 C

0

O H

[ i mark ]

d) Account for the differences in acidity between

ANY ONE

of the pairs of compounds

given below.

EITHER

Ethanol

CH3CH2OH

and phenol

OR

OHO

Phenol (6

and ethanoic

acid CH3

O H

[ 2 marks]

Total 10 marks




14

MODULE 3

Answer ALL questions

7. (a) Explain what is meant by ̀ calibration .

[ l mark]

(b) Distinguish between ̀ precision' and ̀ accuracy' of measurements.

[ 2 marks]

Table 3 below shows the readings obtained during the calibration of a 25 cm3 pipette. During the

calibration exercise the masses of 25 cm3 samples of water were recorded. The volumes of the

equilibrated water used were then determined using the density of water with a correction for

buoyancy error.

TABLE 3: CALIBRATION READINGS

Sample

Volume cm)

25 8

2

25 6

25 17

4 25 1

5 25.009

6 25.015

7 25.007

8 25.008

9

25.015

1

25.006

(c) Using the data in Table 3, calculate the following:

(i) Mean volume delivered by the pipette

(ii) Standard deviation

[ 4 marks]





16

(c) Select any chromophores in methyl salicylate, P, that could be responsible for the absorp-

tion at this wavelength.

OH

COOCH3

P

[ 2 marks]

(d) Methyl salicylate, (P), can be extracted from the plant

Gaultheria fragrantissima. A

10.0 g sample of dried and powdered bark was subjected to solvent extraction using ethyl

acetate. The volume of extract was then reduced and separation techniques used to obtain

a sample of P in solution. A 1 cm3 sample of the final solution containing P showed an

absorbance of 0.85 at a wavelength of 240 nm (absorptivity constant = 12000) and 1 cm

cell path.

(i) Use Beer-Lambert's Law to calculate the molar concentration of methyl salicylate

in the 1 cm3 of solution.

[ l mark]

(ii) Calculate the mass concentration of methyl salicylate in the solution.

[ 2 marks]

(iii) Given that the total volume of the final solution containing P was 10 cm3 , calculate

the percentage of methyl salicylate in the plant sample.

[ 2 marks

Total 10 marks




17

9. Chromatography can be used to separate mixtures of organic or inorganic molecules.

Chromatographic methods involve the use of a mobile phase and a stationary phase.

(a) State the general principle upon which chromatography is based.

[ 1 mark ]

(b) Describe and give ONE example of (i) mobile and (ii) stationary phase.

(i) mobile phase

Example

[ 2 marks]

(ii) stationary phase.

Example

[ 2 marks]




18

(d) The chromatogram below was obtained on analysis of a liquid, A, by elution chromato-

graphy.

Time

Z

(i) Use the chromatogram to comment on the nature of A.

[ 3 marks]

(ii) Explain the difference in the retention times of Y and Z.

[ 2 marks]

Total 10 marks

END OF TEST

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2003 cape chem unit 01 paper 01.PDF