Copper used for electrical wires must be very pure. Impure copper is purified by electrolysis. One electrode is a large block of impure copper and the other is a thin sheet of pure copper. The electrolyte is copper sulfate solution.
State which electrode is made of impure copper.
Describe what happens to the mass of each electrode during the electrolysis.
Impurities collect under one electrode as a sludge. The sludge contains silver and gold. Suggest why the sludge is collected.
Give one reason why copper for electrical wires needs to be pure.
The electrolysis of copper sulfate solution is repeated using graphite electrodes. A gas forms at the anode.
Name the gas.
Describe the test for this gas. Give the result.
52 exam-style questions on Edexcel GCSE Chemistry 4.2 Electrolytic processes, covering 4.2.1 Electrolytes and the process of electrolysis, 4.2.2 Products of electrolysis using inert electrodes, 4.2.3 Half equations, oxidation and reduction in electrolysis, and 4.2.4 Electrolysis of copper sulfate and purifying copper. Each one has a worked solution and a mark scheme showing where the marks go.