Show — 5 marks
A manufacturing company uses electrolysis to extract copper from impure copper ore. They use an electrolytic cell with an impure copper anode, a pure copper cathode, and copper sulfate solution as the electrolyte. The process is essential for producing high-purity copper for electrical wiring.
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Show that the impure copper anode decreases in mass during electrolysis.
[2 marks]
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Show the equation for the reaction occurring at the cathode during this process.
[2 marks]
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Show why less reactive impurities (such as silver) fall to the bottom of the electrolytic cell as 'anode mud' rather than being oxidized.
[1 mark]
Show mark scheme
State — 3 marks
A student carries out an electrolysis experiment using copper sulfate solution with copper electrodes. An electric current is passed through the solution for several minutes.
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State what happens to the mass of the positive electrode (anode) during electrolysis.
[1 mark]
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State the name of the electrode where reduction occurs during electrolysis.
[1 mark]
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State two factors that would increase the rate of electrolysis in this experiment.
[1 mark]
Show mark scheme
State — 3 marks
A student carries out an electrolysis experiment using copper sulfate solution with copper electrodes. A direct current power supply is connected to the electrodes, and the student observes changes at both the positive and negative electrodes during the experiment.
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State the name of the electrode connected to the positive terminal of the power supply.
[1 mark]
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State what is observed at the negative electrode during the electrolysis of copper sulfate solution with copper electrodes.
[1 mark]
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State why the copper electrode connected to the positive terminal gradually decreases in mass during this electrolysis.
[1 mark]
Show mark scheme
Suggest — 5 marks
A jeweller uses electrolysis to coat a steel ring with a thin layer of silver. The steel ring is placed in a solution of silver nitrate. A silver electrode is used as the anode and the steel ring acts as the cathode. A direct current power supply is connected to complete the circuit.
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Suggest why a silver electrode is used as the anode rather than an inert electrode such as platinum.
[2 marks]
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During the electrolysis, silver ions are reduced at the cathode. Write the ionic equation for this reduction reaction.
[1 mark]
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Suggest two ways the jeweller could increase the thickness of the silver coating on the steel ring.
[2 marks]
Show mark scheme
Calculate — 2 marks
A company uses electrolysis to purify copper for making electrical cables. During this process, a current of 4 A is passed through copper sulfate solution for 20 minutes. Copper ions from the solution are deposited as pure copper metal at the negative electrode.
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(01.1) Calculate the total charge, in coulombs, that passes through the solution. Use the equation: charge = current × time
[1 mark]
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(01.2) 0.1 g of copper is deposited when 300 C of charge passes through the solution. Calculate the mass of copper deposited during the 20 minutes.
[1 mark]
Show mark scheme
- (01.1) charge = 4 × (20 × 60)
- (01.1) = 4800 C
- (01.2) 4800 ÷ 300 = 16
- (01.2) 0.1 × 16 = 1.6 g
GCSE Perfect