233. Why is the equilibrium constant k related to only E°_cell and not E_cell.

Nernst equation is given as:
E_cell = ${\mathrm{E}}_{\mathrm{cell}}^{°}-\frac{\mathrm{RT}}{\mathrm{nF}}\mathrm{InQ}$
Where Q  reaction quotient
E_cell is the cell potential at the temperature of interest.
$E_{\mathrm{cell}}^0$ is the standard cell potential 
R is the universal gas constant 
T is the abolute temperture 
F is the Farday constant 
n i the number of electron 
At equilibrium 
E_cell =0 and Q=k
K isthe equilibrium constant

0= ${\mathrm{E}}_{\mathrm{cell}}^{°}-\frac{\mathrm{RT}}{\mathrm{nF}}\mathrm{In}k$

$\mathrm{In} \mathrm{k} =\frac{{\mathrm{nFE}}_{\mathrm{cell}}^0}{\mathrm{RT}}$