Question

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 ?

Answer 1

(a) Positively charged carbon electrode (Anode)

(b) This 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.