a$)$ From the data given in figure $3\mathrm{.}4\mathrm{.}5,$ estimate $i_0$ for the reduction of IV$)$ to $Mn($III$)$ on

platinum in $7\mathrm{.}5$M $H_{2}S{O}_4$ containing $0\mathrm{.}353MMn(III)$ and $0\mathrm{.}4M($IV$).$ The platinum

microelectrode is $0\mathrm{.}8mm$ in diameter.

b$)$ Estimate the limiting current density for the reduction of $Mn(IV)$ to III$)$ on platinum

at $298K$ in $7\mathrm{.}5M{H}_{2}S{O}_4$ containing ${10}^{-2}MMn($III$)$ and ${10}^{-3}MMn(IV).$

c$)$ Estimate the overpotential at which the current for the reduction of IV$)$ to $Mn($III$)$

on platinum at $298K$ in $7\mathrm{.}5M{H}_{2}S{O}_4$ containing ${10}^{-2}MMn(III)$ and ${10}^{-3}MMn(IV)$ has a

value of $3\mathrm{.}53i_0.$