Electrolysis (Cambridge (CIE) IGCSE Chemistry)

Exam Questions

4 hours46 questions
1a1 mark

Electricity was passed through molten lead(II) bromide using the apparatus shown.

The formation of a brown gas was observed at the positive electrode.

molten-lead-bromide-electrolysis

Give one other expected observation.

1b2 marks

i) Name a non-metal that could be used for the electrodes.

 [1]

ii) Suggest why iron is not used for the electrodes.

[1]

1c2 marks

i) Name the brown gas formed

 [1]

ii) Suggest the result of testing this gas with damp blue litmus paper.

[1]

1d1 mark

Name the product formed at the negative electrode.

1e1 mark

State one safety precaution that should be used when doing this experiment.

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2a1 mark

Electricity was used to break down dilute sulfuric acid using the apparatus shown.

dilute-sulfuric-acid-electrolysis

What name is given to this process?

2b1 mark

Give one observation which could be made during this experiment.

2c1 mark

Suggest a suitable metal for the inert metal electrodes.

2d2 marks

Give a test for oxygen gas.

test .............................................................................................. result ...........................................................................................

2e1 mark

Why does hydrogen form at the negative electrode?

2f2 marks

The experiment was repeated using concentrated hydrochloric acid. Explain why this experiment was carried out in a fume cupboard.

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3a2 marks

Electricity was passed through a solution of concentrated hydrochloric acid using the apparatus shown.

concentrated-hcl-electrolysis

Complete the boxes to identify the parts of the apparatus labelled.

3b2 marks

Describe the test for hydrogen.

test ......................................................................................................... result  ....................................................................................................

3c2 marks

Describe how a sample of the gas given off at the positive electrode could be collected and its volume measured.

3d2 marks

The experiment was repeated using a concentrated aqueous solution of sodium chloride instead of hydrochloric acid.

i) State the name of the solution formed.

[1]

ii) Give a test to show the presence of this product.

[1]

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4a1 mark

Electricity was passed through aqueous copper(II) sulfate using inert electrodes as shown in the diagram below. Copper was deposited at one of the electrodes.

aqueous-copper-sulfate-electrolysis

Name a suitable material for the electrodes.

4b1 mark

At which electrode was copper deposited?

4c1 mark

Give one other observation seen during the electrolysis.

4d2 marks

The electrode at which copper was deposited was removed at intervals, washed, dried and weighed. The results are shown below.

time / min

mass of electrode / g

total increase in mass / g

0

3.75

0.00

10

4.00

0.25

20

4.25

0.50

30

4.50

 

40

4.75

 

50

4.90

 

60

4.90

 

70

4.90

 

i) Suggest how the electrode was washed?

[1]

ii) How could the electrode be dried quickly?

[1]

4e1 mark

Complete the table from part d) by calculating the total increase in mass for the remaining time intervals.

4f3 marks

Plot the points on the grid below. Draw a graph with two intersecting straight lines.

h5oIV9~Y_electrolysis-data-graph
4g1 mark

Suggest why the last three readings were the same.

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5a1 mark

A concentrated solution of sodium chloride was electrolysed using the apparatus below.

4-1-q5a

One observation noted was that the Universal Indicator turned purple at the negative electrode.

What observation would be made at both electrodes?

5b1 mark

Why did the indicator turn purple at the negative electrode?

5c2 marks

i) Name the product formed at the positive electrode.

 [1]

ii) Suggest the effect of this product on the Universal Indicator.

 [1]

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6a2 marks

The diagram shows an experiment to pass electricity through lead bromide.

Electricity has no effect on solid lead bromide

heating-lead-bromide

i) Clearly label the electrodes on the diagram.

[1]  

ii) Suggest a suitable material to make the electrodes.

[1]

6b2 marks

Give two observations expected when the lead bromide is heated to melting point.

6c2 marks

State two different safety precautions when carrying out this experiment.

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7a1 mark

Electricity was passed through a concentrated solution of sodium chloride containing Universal Indicator. 

V2Un2QE2_4-1-q5a

Suggest a suitable material for the electrodes. 

7b2 marks

Three observations were noted:

  1. Bubbles of gas seen immediately at the negative electrode.

  2. Bubbles of gas formed after some time at the positive electrode.

  3. The solution turned blue around the negative electrode and colourless near the positive electrode.

Give a test to show that the gas observed in 1 is hydrogen.

test ........................................................................................

result .....................................................................................

7c1 mark

Suggest why bubbles of gas were not seen immediately in 2.

7d2 marks

What causes the colour change in 3 at:

the negative electrode ...........................................................................................

the positive electrode? ...........................................................................................

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8a1 mark

The diagram shows the apparatus used to find out the effect of an electric current on a concentrated aqueous solution of sodium chloride. 

electrolysis-quipment

On the diagram label the electrodes.

8b3 marks

Give three observations when the circuit is switched on.

8c3 marks

i) Name the product at the positive electrode (anode).

[1]

ii) State a test for this product and the result of the test.

[2]

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9a1 mark

Lead bromide was placed in a tube and connected to an electrical circuit as shown below.  

SlygNODk_heating-lead-bromide

The lead bromide was heated until molten. A brown gas was given off.

State one other expected observation.

9b2 marks

i) Suggest a suitable material for the electrodes.

[1]

ii) Indicate on the diagram the negative electrode (cathode).

[1]

9c2 marks

Name the brown gas. At what electrode will the gas be given off?

name ........................................................................

electrode ..................................................................

9d1 mark

Why is this experiment carried out in a fume cupboard?

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10a3 marks

The diagram shows the effect of passing electricity through concentrated hydrochloric acid. 

5-1-q10a

 

Label the diagram by completing the boxes. 

10b1 mark

Name this process.

10c2 marks

Give a test for chlorine.

test

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

result

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

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