b
\(C{u^{ +  + }}\, + \,{e^ - }\, \to \,C{u^ + }\)

\(E_1^o\, = \,0.15\,\,V;\)       \(\Delta G_1^o\, = \, - \,{n_1}E_1^oF\)

\(C{u^{2 + }}\, + \,2e\, \to \,Cu\)

\(E_2^o\, = \,0.34\,V;\)         \(\Delta G_2^o\, = \, - \,{n_2}E_2^oF\)

On subracting eq.\((i)\) from eq. \((ii)\) we get

\(C{u^ + }\, + \,{e^ - }\, \to \,Cu;\)      \(\Delta {G^o}\, = \,\Delta G_2^o\, - \,\Delta G_1^o\,\)

\( - n{E^o}F\, = \, - \,({n_2}{E^o}F\, - \,{n_1}E_1^oF)\)

\({E^o}\, = \,\frac{{\,{n_2}{E^o}F\, - \,{n_1}E_1^oF}}{{nF}}\)

\( = \,\frac{{\,2 \times 0.34 - 0.15}}{1}\)

\(=\,0.53\,V\)