Question

Given, standard electrode potentials
`Fe^(2+) +2e^(-) rarr Fe, E^(@)=-0.440 V`
`Fe^(3+)+3e^(-) rarr Fe, E^(@)=- 0.036 V`
The standarde potential `(E^(@))` for
`Fe^(2+)+e^(-) rarr Fe^(2+)`, is
A. `+0.772` V
B. `-0.772` V
C. `+0.589 V`
D. `-0.589 V `

Answer 1

Correct Answer - A
`Delta G = - n E_(cell) F`
`Fe^(2+) + 2e^(-) to Fe`
`Delta G_(1)^(@) = - 2 F xx (-0.44 V) = 0.880 F " " … (i)`
`Fe^(3+) + 3 e^(-) to Fe`
`Delta G_(2)^(@) = - 3 xx F xx (-0.036 V) = 0.108 F " " … (ii)`
Substracting Eq(i) and (ii)
`Fe^(3+) + 3e^(-) to Fe^(2+)`
`Delta G^(@) = 0.108 F - 0.880 F = -0.772 F`
`E^(@) = (DeltaG^(@))/(-nF) = (-0.772 F)/(-n F) = (0.772)/(1) = 0.772 `V