Question

The standard reduction potential of $C{u}^{2+}/Cu$ couple is $0.34$V at ${25}^0$C. Calculate the reduction potential at $pH=14$ for this couple.
Given $K_{sp}$ of $Cu(OH{)}_2=1.0\times {10}^{-18}$)

Answer 1

$E_{cell}=E^0-\frac{0.059}{2}log\left[\frac{1}{{Cu}^{2+}}\right]$

given $pH=14$ $pOH=0$

$\therefore {\left[OH\right]}^{-}=-log\left(0\right)=1M$

$K_{sp}=\left[{Cu}^{2+}\right]\left[{OH}^{-}\right]$

$\therefore \left[{Cu}^{2+}\right]=\frac{K_{sp}}{\left[{OH}^{-}\right]}=1\times {10}^{-18}$

$E_{cell}=0.34-\frac{0.059}{2}log\left[{10}^{18}\right]=-0.191V$