Given that : `E_(Ni^(2+)|Ni)^(@)=-0.25V,`
`E_(Cd^(2+)|Cd)^(@)=-0.40V, e_(Fe^(2+)|Fe)^(@)=-0.44V,`
`E_(Cu^(2+)|Cu)^(@)=+0.34V, E_(Fe^(3+)|Fe)^(@)=-0.036V,`
`E_(2H^(+)|H_(2))^(@)=0.00V, E_(I_(2))|(2I^(-))^(@)=+0.80V`
Select appropriate species in each of the following cases :
`Ni^(2+)` is reduced but not `Fe^(2+)`

Explanation

The higher the standard reduction potential of an electrode or a half - cell, the greater is the tendency of its oxidised from to get reduced.
(1) As `E_(Cd^(2+)|Cd)^(@) lt E_(Ni^(2+)|Ni)^(@) and E_(Fe^(2+)|Fe)^(@) lt E_(Cd^(2+)|Cd)^(@)`,
`Ni^(2+)`, but not `Fe^(2+)`, will be reduced by Cd. Hence, the appropriate species is Cd.