$E_1^o\, = \,0.15\,\,V;$ $\Delta G_1^o\, = \, - \,{n_1}E_1^oF$
$C{u^{2 + }}\, + \,2e\, \to \,Cu$
$E_2^o\, = \,0.34\,V;$ $\Delta G_2^o\, = \, - \,{n_2}E_2^oF$
On subracting eq.$(i)$ from eq. $(ii)$ we get
$C{u^ + }\, + \,{e^ - }\, \to \,Cu;$ $\Delta {G^o}\, = \,\Delta G_2^o\, - \,\Delta G_1^o\,$
$ - n{E^o}F\, = \, - \,({n_2}{E^o}F\, - \,{n_1}E_1^oF)$
${E^o}\, = \,\frac{{\,{n_2}{E^o}F\, - \,{n_1}E_1^oF}}{{nF}}$
$ = \,\frac{{\,2 \times 0.34 - 0.15}}{1}$
$=\,0.53\,V$
[આપેલ : $1\,F =96500\,C\,mol ^{-1},$ $Fe$નું પરમાણ્વીય દળ $= 56\,g\,mol ^{-1}$ ]
[Cuનું મોલર દળ : $63 \mathrm{~g} \mathrm{~mol}^{-1}, 1 \mathrm{~F}=96487 \mathrm{C}$ આપેલ છે.]
$Pt _{( s )}\left| H _2( g , 1\,atm )\right| H ^{+}( aq , 1 M )|| Fe ^{3+}( aq ), Fe ^{2+}( aq ) \mid Pt ( s )$
$298\,K$ પર જયારે કોષ નો પોટેન્શિયલ $0.712\,V$ હોય તો $\left[ Fe ^{2+}\right] /\left[ Fe ^{3+}\right]$ નો ગુણોત્તર $.......$ છે.
આપેલ:$Fe ^{3+}+ e ^{-}= Fe ^{2+}, E ^{\circ} Fe ^{3+}, Fe ^{2+} \mid Pt =0.771$
$\frac{2.303 RT }{ F }=0.06\,V$