Aluminium oxide may be electrolysed at 1000oC to furnish aluminium metal (Atomic Mass = 27 amu; 1F = 96,500 C). The cathode reaction is Al3++3e−→AlTo prepare 5.12 kg of aluminium metal by this method would require

27 g of Al is obtained by passing a current of 3×96500 C.∴ 1 g of Al is obtained by passing a current of 3×9650027C. ∴ 5.12×103 g of Al is obtained by passing a current of 3×9650027×5.12×1000                       =1.83×107C×3=5.49×107C