Given,`{:(E_(Fe^(3+) //Fe)^o + 3e Cr E^o =- 0.036 V),(E_(Fe^(3+) //Fe)^o =- 0.439 V):}`
The value of standard electrode ptoential for the charge,

Options

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

Answer

C

Explanation

`Fe^(3+)+3e^(-)rarrFe,E^(@)=-0.036V`
`DeltaG_(1)^(0)=-nFE^(@)=-3xxFxx(-0.036)=0.108F`
Also `Fe^(2+)+2e^(-)rarrFe,E^(@)=-0.439V`
`thereforeDeltaG_(2)^(0)=-2xxFxx(-0.439)=0.878F`
For `Fe_((aq.))^(3+)+e^(-)rarrFe_((aq.))^(2+)`
`DeltaG^(0)=-1xxFxxE^(@)`
`becasue DeltaG^(0)=Delta_(1)^(0)-Delta_(2)^(0)`
`therefore-FxxE^(@)=0.108F-0.878F`
`E^(@)=0.77V`