Answer:
4.0921 is the logarithm of the equilibrium constant.
Step-by-step explanation:
; E° = - 0.41 V
; E° = 0.80 V
Iron having negative value of reduction potential .So ,that means that it will loose electron easily and get oxidized.Hence, will be at anode.
=Reduction potential of cathode - Reduction potential of anode


; E° = - 0.41 V
; E° = 0.80 V
Net reaction: 
n = 2
To calculate equilibrium constant, we use the relation between Gibbs free energy, which is:

and,

Equating these two equations, we get:

where,
n = number of electrons transferred = 2
F = Faraday's constant = 96500 C
= standard electrode potential of the cell = 1.21 V
R = Gas constant = 8.314 J/K.mol
T = temperature of the reaction = ![25^oC=[273+25]=298K](https://tex.z-dn.net/?f=25%5EoC%3D%5B273%2B25%5D%3D298K)
Putting values in above equation, we get:



4.0921 is the logarithm of the equilibrium constant.