\(\mathrm{MnO}_{4}^{2-} \longrightarrow \mathrm{MnO}_{4}^{-}+e^{-}\)
\(0.1 \mathrm{mol}\quad \quad \quad \quad \;\;\quad1 \mathrm{mol}\)
\(Q=0.1 \times F=0.1 \times 96500 \mathrm{C}=9650 \mathrm{C}\)
$(A)$ $Sn^{+4}+ 2e^{-} \rightarrow Sn^{2+}$, $E^o= + 0.15\,V$
$(B)$ $2Hg^{+2} + 2e^{-} \rightarrow Hg_{2}^{+2}$, $E^o = + 0.92\,V$
$(C)$ $PbO_2 + 4H^{+} + 2e^{-} \rightarrow Pb^{+2} + 2H_2O$, $E^o = + 1.45\,V$