`E_(Fe^(3+)//Fe)^(@)=-0.036V,E_(Fe^(2+)//Fe)^(@)=-0.0439V`. The value of standard electrode potential for the change, `Fe^(3+)(aq)+e^(-)toFe^(2+)(aq)` will be

Options

A. `-0.072 V`
B. `0.385 V`
C. `0.770 V`
D. `-0.270 V`

Answer

A

Explanation

Given `Fe^(3+) +3e^(-) rarr Fe, E_(1)^(@) =- 0.036 V`
`Fe^(2+) +2e^(-) rarr Fe, E_(2)^(@)=- 0.439V`
We need to calculate
`Fe^(3+) +e^(-) rarr Fe^(2+), E_(3)^(@) =?`
`triangle G_(3) = triangle G_(2) (triangle "G is an extensive property")`
`triangle G_(3) =3xx0.036V-2xx0.0439 V`
`triangle G_(3) =0.108 V - 0.878 V`
`-1 xxV xxE_(3) =- 0.770 V`
`E_(3)^(@) =0.770 v`