Question

The role of coke in the electrolytic reduction of alumina is to:

• A. provide heat for melting of alumina
• B. prevent loss of heat
• C. prevent burning of carbon rods
• D. reduce alumina to metal

Answer 1

Answer: (C)

prevent burning of carbon rods

In extraction of aluminium following reaction takes place:

$2{Al}_2{O}_3⟶4Al+3O_2$

Oxygen is given off at the positive carbon anode. Carbon dioxide is also given off at the anode because hot oxygen reacts with the carbon anode to form carbon dioxide gas.

$C+O_2⟶{CO}_2$

The carbon anodes slowly disappear because each molecule of carbon dioxide which is given off takes a little piece of carbon away with it.

Hence, The role of coke in the electrolytic reduction of alumina is to prevent burning of carbon rods.