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

Answer

For the reaction
`2CI^(-) (aq) +2H_(2)O (I) rarr 2OH^(-) (aq) +H_(2)(g) + CI_(2)(g)`
Value of `DeltaG^(@)` is `+422 kJ`. Using the equation `DeltaG^(Theta) =- nFE^(Theta)` the value of `E^(Theta)` comes out to be `-2.2V` Therefore extraction of `CI_(2)` from brine will require an external emf of greater than `2.2V`.