Why is an external emf of more than `2.2V` required for the extraction of `Cl_(2)` from brine?

Explanation

For the reaction of extraction of `Cl_2` from brine solution : `2Cl^(-) (aq) + 2H_2 O (l) to 2OH^(-) (aq) + H_2 (g) + Cl_2 (g)`
The value of `DeltaG^(ө)` is `+ve` (`422 kJ`). For this the value of `E^(ө)` is
`DeltaG^(ө) =-nFE^(@)`
or `E^@ = -(DeltaG^(ө))/(nF) =-(422 xx 10^(3)J)/(2xx96500) =-2.20 V`
Therefore, extraction of `Cl_2` from brine solution will require an external e.m.f more than `2.20V` for electrolysis process.