On diluting the concentration of ${\mathrm{Cl}}^{-}$ ions by ten times in a calomel cell, its potential at 298 K is

The reaction to be considered is ${\mathrm{Hg}}_2{\mathrm{Cl}}_2+2{\mathrm{e}}^{-}⟶2\mathrm{Hg}+2{\mathrm{Cl}}^{-}$. Its Nemst equation is

$E_1=E^{\circ }-\frac{RT}{2F}\ln {\left[{\mathrm{Cl}}^{-}\right]}^2$

On diluting the concentration of ${\mathrm{Cl}}^{-}$ by ten times, we have

$E_2=E^{\circ }-\frac{RT}{2F}\ln \left\{\left(0.01\right){\left[{\mathrm{Cl}}^{-}\right]}^2\right\}$

Hence  $E_2-E_1=-\frac{RT}{2F}\ln \left(0.01\right)=\frac{RT}{F}=0.059\mathrm{V}$