\(Ksp =\left[ Cu ^{2+}\right]\left[ OH ^{-}\right]^2\)

\(pH =14 ; pOH =0 ;\left[ OH ^{-}\right]=1\,M\)

\({\left[ Cu ^{2+}\right]=\frac{ Ksp }{[1]^2}=10^{-20} M }\)

\(Cu ^{2+}( aq )+2 e ^{-} \rightarrow Cu ( s )\)

\(E = E ^{\circ}-\frac{0.059}{2} \log _{10} \frac{1}{\left[ Cu ^{2+}\right]}\)

\(=0.34-\frac{0.059}{2} \log _{10} \frac{1}{10^{-20}}\)

\(=-0.25=-25 \times 10^{-2}\)