If `E_(1)^(0)`is standard electron potential for `Fe//Fe^(+2)` and `E_(2)^(0)` is for `Fe^(+2)//Fe^(+3)` and`E_(3)^(0)` for `Fe//Fe^(+3)` which of the following relation is correct?

Options

A. `E_(3)^(0)=E_(1)^(0)+E_(2)^(0)`
B. `E_(3)^(0)=(E_(1)^(0)+E_(2)^(0))//2`
C. `E_(3)^(0)=E_(2)^(0)+2E_(1)^(0)`
D. `E_(3)^(0)=(E_(2)^(0)+2E_(1)^(0))//3)`

Answer

D

Explanation

`FetoFe^(+2)+2e -/_\G_(1)^(0)=2xxE_(1)^(0)xxF`…….(i)
`Fe^(+2)toFe^(+3)+e -/_\G_(2)^(0)=1xxE_(2)^(0)xxF`……(ii)
`FetoFe^(3+)+3e -/_\G_(3)^(0)=3xxE_(3)^(0)xxF`…..(iii)
Substracting equation (i) from equation (ii), we get
`Fe^(+2)toFe^(+3)+e`
`/_\G_(3)^(0)+/_\G_(3)^(0)+/_\G_(1)^(0)`
`E_(2)^(0)F=3E_(3)^(0)F-2E_(1)^(0)F`
`E_(3)^(0)=(E_(2)^(0)+2E_(1)^(0))//3`