Which is a stronger reducing agent `Cr^(+2)` or `Fe^(+2)` and why ? `E^(@)(Cr^(+3)//Cr^(+2))=-0.4//V` and `E^(@)(Fe^(+3)//Fe^(+2))` is 0.77V.

Explanation

In general, for the reduction reaction
`M^(n+)+ne to M`,
Larger the value of standard reduction potential, greater the extent to which `M^(n+)` is reduced to M. i.e., `M^(n+)` acts as an oxidising agent. Compare
`Cr^(+3)+e to Cr^(+2) E^(@)=-0.41V`
`Fe^(+3)+e to Fe^(+2) E^(@)=0.77V`.
The negative value indicates that `Cr^(+2)` is readily oxidised to `Cr^(+3)` i.e., it is a stronger reducing agent than `Fe^(+2)`.