In an electrolytic tank, aluminium metal is being extracted by the electrolysis of molten aluminium oxide using carbon electrodes. It is observed that one of the carbon electrodes is gradually burnt away and has to be replaced. (a) Which carbon electrode (cathode or anode) is burnt away? (b) Why is this carbon electrode burnt away?

Question

Philoid · Accepted Answer

(a) The carbon electrode (cathode or anode) is burnt away is positively charged carbon electrode(Anode).

(b) The carbon electrode is burnt away because oxygen produced during the electrolysis of molten aluminium oxide reacts gradually with the carbon of carbon anode to form carbon dioxide gas.