In the conductometric titration of ${\mathrm{CH}}_3\mathrm{COOH}$ vs $\mathrm{NaOH}$, the titration curve obtained will be of the type:

${\mathrm{Fe}}^{2+}+2\mathrm{e}\to \mathrm{Fe}...\left(\mathrm{i}\right)$

${\mathrm{Fe}}^{3+}+\mathrm{e}\to {\mathrm{Fe}}^{2+}...\left(\mathrm{ii}\right)$

The standard potentials (in volt) corresponding to the reactions $\left(\mathrm{i}\right)$ and $\left(\mathrm{ii}\right)$ are ${\mathrm{E}}_1$ and ${\mathrm{E}}_2$ respectively. The value (in volt) of the standard potential corresponding to the reaction ${\mathrm{Fe}}^{3+}+3\mathrm{e}\to \mathrm{Fe}$ is:

In an alkaline energy cell the overall cell reaction is as follows:

$\mathrm{Zn}\left(\mathrm{s}\right)+2{\mathrm{MnO}}_2\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{Zn}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+2\mathrm{MnO}\left(\mathrm{OH}\right)$

Which of the following reactions is taking place at the cathode?