Why must the positive electrode be replaced regularly in the extraction of aluminium?
The molten cryolite slowly dissolves the carbon of the electrode
The aluminium formed coats the electrode and stops the current
The large current melts the carbon and it drips into the cell
The oxygen formed reacts with the carbon to make carbon dioxide
40 exam-style questions on AQA GCSE Chemistry 4.3 Electrolysis, covering 4.3.1a The process of electrolysis, 4.3.1b Half equations in electrolysis, 4.3.2 Electrolysis of molten ionic compounds, 4.3.3 Using electrolysis to extract metals, 4.3.4 Electrolysis of aqueous solutions, and 4.3.5 Representation of reactions at electrodes as half equations. Each one has a worked solution and a mark scheme showing where the marks go.