Explain why the positive carbon electrodes must be continually replaced.[3 marks]

The positive carbon electrodes, also known as anodes, are involved in the electrolysis process where they react with oxygen to form carbon dioxide. This reaction is a part of the process of producing metals like aluminium.

This reaction is a combustion reaction, which means the carbon electrodes are gradually burnt away during the process. This is why they need to be continually replaced.

Additionally, the quality of the electrolysis process can be affected if the electrodes are not replaced regularly. Worn out or damaged electrodes can lead to inefficiencies in the process or even cause it to stop. Therefore, to maintain the efficiency and continuity of the process, the positive carbon electrodes must be continually replaced.