Reaction at the anode in electrolysis of molten alumina:

• a$\ce{2Al^3+ + 6e- -> 2Al}$
• b$\ce{3O^2- -> O2 + 6e-}$ (with stoichiometric balance for 2 mol O2)
• c$\ce{Al^3+ -> Al}$
• d$\ce{O2 + 4e- -> 2O^2-}$