4024q3Specimen

Extracted Content: 4024q3Specimen

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ZIMBABWE SCHOOL EXAMINATIONS COUNCIL

General Certificate of Education Ordinary Level
CHEMISTRY 4024/3
PAPER 3 Practical Test

SPECIMEN PAPER 1 hour 30 minutes

Candidates answer on the question paper.
Additional materials:
As listed in Instructions to Supervisors
Mathematical tables and/or Electronic calculator

TIME 1 hour 30 minutes

INSTRUCTIONS TO CANDIDATES

Write your name, Centre number and candidate number in the spaces at the top of this page.
Answer both questions.

Write your answers in the spaces provided on the question paper.

Y ou should show the essential steps in any calculation and record all experimental results in the
spaces provided on the question paper.

INFORMATION FOR CANDIDATES
The number of marks is given in brackets [ ] at the end of each | FOR EXAMINER’S USE
question or part question.
Qualitative analysis notes for this paper are printed on page 6. 1

2

3

TOTAL

This question paper consists of 6 printed pages and 2 blank pages.

Copyright: Zimbabwe School Examinations Council, Specimen paper.
©ZIMSEC [Turn over

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Y ou are required to determine the concentration of sodium hydroxide in g/dm?
of solution using 0.1 moldm‘® of nitric acid.

Solution $ is 0.1 moldny® nitric acid, HNO3(aq)

Solution R is aqueous sodium hydroxide, NaO Haq)

Using a pipette, transfer 25 cm? of solution R into a conical flask.
Add 2 to 3 drops of phenolphthalein indicator.

Fill the burette with solution S.

Titrate solution R with S.

Repeat the titration as many times as you consider necessary to obtain accurate
results.

(a) Record your results in Table 1.1.

Table 1.1

titration number 1 2 3

final burette reading /cm?

initial burette reading /cm?

volume of acid used /cm?

tick the best results

Summary

25.0 cm? of R required cm} of S.

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(b) Write a balanced chemical equation for the reaction.

() Calculate

@ the number of moles of HNO; that reacted with 25.0 cm? of
NaOH,

di the number of moles of NaOH in 25 cm?,

(iii) concentration of NaOH in moldm’’.

[1]

@ Hence express the concentration of NaOH in g/dm3
[MrNaOH =40]

[1]
[Total:20]

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4

Y ou are required to investigate the effect of concentration on the rate of
reaction between dilute nitric acid and sodium thiosulphate solution. The
time taken for the quarry stone to become invisible will be noted

Experiment 1

Using a measuring cylinder, place 45 cm? of sodium thiosulphate solution
in aconical flask. Place a quarry stone, the size of a pea, in the flask.

Add 5 cm? of 0.5 mol/dm’ of nitric acid in the flask and at the same time
start the stop watch.

Observe, from above, the time taken for the stone to become invisible.
@ Record the time taken in Table 2.1
Experiment 2

Repeat experiment 1 using 30 cm? of sodium thiosulphate, 15 cm?
of distilled water and 5 cm? of nitric acid,

Experiment 3

Repeat experiment 1 using 20 cm? of sodium thiosulphate, 25 cm?
of distilled water and 5 cm? of nitric acid.

Table 2.1

experiment
number

volume of
thiosulphate/

volume of
nitric acid/

volume of
distilled

time/s

cm3 cm3 water/ cm?

45 5 0

30 5 15

20 5 25

di Draw aconclusion from the results in Table 2.1.

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(b) Solid A contains one cation and one anion.

Carry out the following

ests on Solid A to identify the ions inA.

test

observations deductions

(i) Describe the appearance
of Solid A.

(ii) Add a spatula of solid A

to 10cm? of distilled
water in a boiling tube,
stopper and shake.

(iii) Divide the solution from
(ii) into two equal portions

Use the portions for tests 1
and 2.

1. To the first portion,
add aqueous sodium
hydroxide.

Warm the mixture.

2. To the second portion,
add a few drops of nitri
acid followed by silver
nitrate solution.

To the mixture add
aqueous ammonia

[6]

(iv) Solid A contains

cation and anion. [2]

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QUALITATIVE ANALYSIS NOTES (4024/3)

Tests for anions

anion test test result

carbonate (CO 3 = ) add dilute acid effervescence, carbon

dioxide produced

chloride (Cl ) acidify with dilute nitric acid, white ppt.

[in solution] then add aqueous silver nitrate

iodide (I ) acidify with dilute nitric acid, yellow ppt.

[in solution] then add aqueous lead (II) nitrate

nitrate (NO 3 =) add aqueous sodium hydroxide ammonia produced

[in solution] then aluminium foil; warm
carefully

sulphate (SO 4 = ) acidify with dilute nitric acid white ppt.

[in solution] then add aqueous barium nitrate.

Tests for aqueous cations

cation effect of aqueous sodium effect of aqueous ammonia
hydroxide

aluminium (Al 3h white ppt., soluble in excess white ppt., insoluble in excess giving a
colourless solution

ammonium (NH 4 4 ammonia produced on warming

. 2+, . . .

calcium (Ca™ ) white ppt., insoluble in excess no ppt.

copper (Cu as) light blue ppt., insoluble in light blue ppt., soluble in
excess excess giving a dark blue

solution

iron (II) (Fe ca green ppt., insoluble in excess green ppt., insoluble in excess

iron (III) (Fe 34) red-brown ppt., insoluble in red-brown ppt., insoluble in excess excess

zine (Zn. a white ppt., soluble in excess white ppt., soluble in
giving a colourless solution excess giving a

colourless solution

Tests for gases

gas

test and result

ammonia (NH 4)

tums damp red litmus paper blue

carbon dioxide (CO 2)

tums limewater milky

chlorine (C1 P)

bleaches damp litmus paper

hydrogen (H 2)

“pops” with a lighted splint

oxygen (O 2)

relights a glowing splint

sulphur dioxide (SO 2)

tums aqueous potassium dichromate (V1) from orange to green

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