Give reasons: On the basis of Eo values, O2 gas should be liberated at the anode but it is Cl2 gas which is liberated in the electrolysis of aqueous NaCl.

It is due to the phenomenon of over-voltage. Experimentally, it is observed that the actual voltage required for electrolysis is greater than that calculated from standard potentials. This additional voltage required is called over-voltage. It is required because the rate of transfer of electrons at the interface of the electrode and solution for both half-reactions is slow. The over-voltage required for the formation of oxygen is much larger than that required for the formation of chlorine. Hence, chlorine gas is liberated in the electrolysis of aqueous NaCl.