Ksp of AgCl is ${10}^{-10}{\mathrm{M}}^2$ Electrode potential of Ag/AgCl electrode in contact with 1M KCl at ${25}^{\circ }\mathrm{C}\text{ is }\left({\mathrm{E}}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}^0=+0.8\mathrm{V}\right)$

$\left[{\mathrm{Ag}}^{+}\right] =\frac{{\mathrm{K}}_{\mathrm{sp}}}{\left[{\mathrm{Cl}}^{-}\right]}=\frac{{10}^{-10}}{1}={10}^{-10}$

${\mathrm{Ag}}^{+}+{\mathrm{e}}^{-}\to \mathrm{Ag}$

${\mathrm{E}}_{\mathrm{RP}}={\mathrm{E}}_{\mathrm{RP}}^0-\frac{0.0591}{\mathrm{n}}\log \frac{1}{\left[{\mathrm{Ag}}^{+}\right]}$

${\mathrm{E}}_{\mathrm{RP}}={\mathrm{E}}_{\mathrm{RP}}^0-\frac{0.0591}{\mathrm{n}}\log \frac{1}{{10}^{-10}}$

${\mathrm{E}}_{\mathrm{RP}}=0.8-0.0591\times 10=0.209\cong 0.2$