RP 3 - Electrolysis QP

AQA Chemistry GCSE
Required Practical 3 - Electrolysis

Past Exam Questions
PhysicsAndMathsTutor.com
Q1. What are the products of electrolysing potassium iodide solution?
Tick one box.
Product at cathode Product at anode
Hydrogen Iodine
Hydrogen Oxygen
Potassium Iodine
Potassium Oxygen
(1)
Q2. Diagram 1 shows the apparatus used to electrolyse magnesium sulfate solution.
Diagram 1
Gases were given off at both electrodes.
(a) The gas collected at the anode was oxygen.

Draw one line from the test for oxygen to the correct result.
(1)
(b) (i) The gas collected at the cathode was hydrogen.
Describe how to test the gas to show that it is hydrogen.
Test ......................................................................................................
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Result ....................................................................................................
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(2)
(ii) Why is hydrogen, and not magnesium, produced at the cathode?
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(1)
(c) A student wanted to use electrolysis to silver plate a metal spoon.

(i) Give one reason why metal spoons are sometimes silver plated.
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(1)
(ii) Diagram 2 shows the apparatus the student used. The student did not set the
apparatus up correctly.
Diagram 2 d.c. power supply
The student found that the metal spoon eroded and a thin layer of copper formed on the
pure silver electrode.
Suggest two changes that the student must make to his apparatus to be able to silver
plate the metal spoon. Give a reason for each change.
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(4)
(iii) Why is it difficult to electroplate plastic spoons?
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(1)
Q3. Aluminium is extracted by electrolysis, as shown in Figure 2
Figure 2
(i) Why can aluminium not be extracted by heating aluminium oxide with carbon?
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(1)
(ii) Explain why aluminium forms at the negative electrode during electrolysis.
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(3)
(iii) Explain how carbon dioxide forms at the positive electrodes during electrolysis.
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(3)

RP 3 - Electrolysis QP

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AQA Chemistry GCSE

Required Practical 3 - Electrolysis

Gases were given off at both electrodes.

(a) The gas collected at the anode was oxygen.

(ii) Why is hydrogen, and not magnesium, produced at the cathode?

(c) A student wanted to use electrolysis to silver plate a metal spoon.

Diagram 2 d.c. power supply

(iii) Why is it difficult to electroplate plastic spoons?

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