For the given cell ${\mathrm{Fe}}^{2+}\left(\mathrm{eq}\right)+{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)\to {\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+\mathrm{Ag}\left(\mathrm{s}\right)$
The standard cell potential of the above reaction is
Given :

$\begin{array}{l}{\mathrm{Ag}}^{+}+{\mathrm{e}}^{-}\to \mathrm{Ag}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em} {\mathrm{E}}^0=\mathrm{xV}\\ {\mathrm{Fe}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{Fe}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em} {\mathrm{E}}^0=\mathrm{yV}\\ {\mathrm{Fe}}^{3+}+3{\mathrm{e}}^{-}\to \mathrm{Fe}\hspace{0.25em} \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{E}}^0=\mathrm{zV}\end{array}$

${\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)\to {\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+\mathrm{Ag}\left(\mathrm{s}\right)$

$\begin{array}{l}\begin{array}{rl} & {\mathrm{\Delta G}}_3^0={\mathrm{\Delta G}}_1^0+{\mathrm{\Delta G}}_2^0\\ & -3\mathrm{F}(-\mathrm{z})=-2\mathrm{F}(-\mathrm{y})+{{\mathrm{\Delta G}}_2}^0\\ & {\mathrm{\Delta G}}_2^0=3\mathrm{Fz}-2\mathrm{Fy}\end{array}\\ \text{ Also }{\mathrm{\Delta G}}_2^0=-{\mathrm{nFE}}_{{\mathrm{Fe}}^{+2}/{\mathrm{Fe}}^{+3}}^0\\ 3\mathrm{Fz}-2\mathrm{Fy}=-1\mathrm{F}\left({\mathrm{E}}_{{\mathrm{Fe}}^{+2}/{\mathrm{Fe}}^{+3}}^0\right)\\ {\mathrm{E}}_{{\mathrm{Fe}}^{+2}/{\mathrm{Fe}}^{+3}}^0=2\mathrm{y}-3\mathrm{z}\end{array}$

$\begin{array}{r}{\mathrm{E}}_{\text{Cell }}^0\text{ for reaction will be }\\ \begin{array}{rl} & {\mathrm{E}}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}^0+{\mathrm{E}}_{{\mathrm{Fe}}^{+2}/{\mathrm{Fe}}^{+3}}^0\\ & =\mathrm{x}+2\mathrm{y}-3\mathrm{z}\end{array}\end{array}$