CBSE Class 12 · 2000 · All India Compartment · Redox Reactions and ElectrochemistryVery Short Answer

Why is it that aluminium metal cannot be obtained by electrolysis of an aqueous solution of a salt of aluminium?

Solution

The reduction potential of water is much higher than that of Al

^{3 +}

(

E_{A l^{3 +} /Al}^{\circ} = - 1.66

V).
At the cathode, water is therefore reduced in preference to Al

^{3 +}

, and hydrogen gas is evolved instead of aluminium being deposited. (Aluminium is obtained by electrolysis of molten alumina.)

CBSE Class 12 Board · 2000 · All India Compartment · Subjective