Electrolysis of copper sulphate solution using platinum or carbon electrodes
Copper sulphate solution contains Cu2+ ions and SO/ – ions together with H + and OH – ions from the water.
During electrolysis, Cu2+ and H+ ions: migrate to the cathode, but only the Cu2+ ions are discharged. The H + ions remain in solution. As each Cu2 + ion is discharged it becomes a neutral Cu atom and is deposited on the cathode. After a time, therefore,
the cathode becomes covered with a reddish layer of pure copper. At the anode the action is identical with that which occurs in the case of acidified water described in the previous section. OH – ions are discharged and combine in pairs to give water and oxygen gas. If the current is passed through the electrolyte for. a sufficiently long time all the copper ions are removed from the solution and deposited on the cathode. The. electrolyte therefore loses its blue colour and becomes dilute sulphuric acid. When this stage has been reached the action becomes simply the electrolysis of dilute sulphuric acid. Hydrogen is liberated at the cathode and oxygen at the anode.