Given standard electrode potentials:
`Fe^(3+) +3e^(-) rarr Fe, E^(@) =- 0.036` volt
`Fe^(2+) +2e^(-) rarr Fe, E^(@) =- 0.040` volt
The standard electrode potential `E^(@)` for
`Fe^(3+) +e^(-) rarr Fe^(2)` is:-