May/June 2026 Paper 41

This question is about the effects of electricity on chemical substances. Dilute aqueous sodium chloride decomposes when an electric current is passed through it. Graphite electrodes are used. The products are: • oxygen at the anode • hydrogen at the cathode. Name the process that occurs when an aqueous ionic compound decomposes by the passage of an electric current.

Give two reasons why graphite is suitable for use as an electrode.

Write an ionic half-equation for the formation of hydrogen at the cathode.

Explain why oxygen is produced at the anode.

Name the type of particle responsible for the transfer of charge in the conducting wires of the external circuit.

Name the products formed at each electrode when an electric current is passed through concentrated aqueous sodium chloride.

Aluminium is extracted when electricity is used to decompose an electrolyte containing a purified ore of aluminium. The electrodes are made of carbon. Name the ore of aluminium that is purified.

Name the compound of aluminium that is present in this ore of aluminium.

Name the substance that the compound of aluminium in 5(b)(ii) is dissolved in during this extraction.

Explain why the carbon anodes have to be replaced.