Question

During the electrolytic reduction of aluminium, the carbon anodes are replaced from time to time because

• A. The carbon anodes get decayed
• B. The carbon prevents atmospheric oxygen from coming in contact with aluminium
• C. Oxygen liberated at the carbon anodes reacts with anodes to form CO and CO2
• D. Carbon converts Al2O3 to Al

Answer 1

Answer: (C)

Oxygen liberated at the carbon anodes reacts with anodes to form CO and CO2

Answer 2

Cathode : Al3+ (melt) + 3e–$\longrightarrow$ Al

Anode : C + O2– (melt) $\longrightarrow$ CO + 2e– ; C + 2O2–(melt) $\longrightarrow$ CO2 + 4e–