Which one of Sn, Cu, Cr, Al can reduce `Fe^(2+)` ion in aqueous medium? Explain. The standard reduction potential of `Sn^(2+)|Sn, Cu^(2+)|Cu, Al^(3+)|Al, Cu^(3+)|Cr` and `Fe^(2+)|Fe` electrodes are `-0.14,+0.34, -1.66, -0.74 and -0.44V` repectively.

Explanation

Metals having lower standard reduction potential `(E_(M^(n+)|M)^(@))` then `E_(Fe^(2+)|Fe)^(@)` will have higher tendency to get oxidised compared to `Fe^(2+)` i.e., they will act as stronger reductant than `Fe^(2+)`. Among the given systems both `Al^(3+)|Al` and `Cr^(2+)|Cr` have lower `E^(@)` value than `Fe^(2+)|Fe` system and hence Al and Cu can reduce `Fe^(2+)` in the aqueous medium.