Why carbon and paste of mercury oxide is used as a cathode in mercury cell why?

Which is increasing order of reducing power of the following metals on the basis of standard electrode potential?

${{\mathrm{E}}^{\circ }}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}=0.80 \mathrm{V}, {{\mathrm{E}}^{\circ }}_{{\mathrm{Mg}}^{2+}/\mathrm{Mg}}=-2.37 \mathrm{V}, {{\mathrm{E}}^{\circ }}_{{\mathrm{Hg}}^{2+}/\mathrm{Hg}}=0.79 \mathrm{V}, {{\mathrm{E}}^{\circ }}_{{\mathrm{Cr}}^{3+}/\mathrm{Cr}}=-0.74 \mathrm{V}$

Given below are half cell reactions :

${\mathrm{MnO}}_4^{-}+8{\mathrm{H}}^{+}+5{\mathrm{e}}^{-}\to {\mathrm{Mn}}^{2+}+4{\mathrm{H}}_2\mathrm{O}$,

${\mathrm{E}}_{{\mathrm{Mn}}^{2+}/{\mathrm{MnO}}_4^{-}}^{\mathrm{o}}=-1.510 \mathrm{V}$

$\frac{1}{2}{\mathrm{O}}_2+2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2\mathrm{O}$

${\mathrm{E}}_{{\mathrm{O}}_2/{\mathrm{H}}_2\mathrm{O}}^{\mathrm{o}}=+1.223 \mathrm{V}$

Will the permanganate ion, ${\mathrm{MnO}}_4^{-}$ liberate ${\mathrm{O}}_2$ from water in the presence of an acid?

The value of potential of the cell in which the following reaction takes place at $298 \mathrm{K}$ is

[At $298 \mathrm{K},{\mathrm{E}}^0\left({\mathrm{Ag}}^{+}/\mathrm{Ag}\right)=+0.80 \mathrm{V};{\mathrm{E}}^0\left({\mathrm{Al}}^{3+}/\mathrm{Al}\right)=-1.66 \mathrm{V};2.303\mathrm{RT}/\mathrm{F}=0.06 \mathrm{V}$ ]

$\mathrm{Al}\left(\mathrm{s}\right)+3{\mathrm{Ag}}^{+}(0.001\mathrm{M})\to {\mathrm{Al}}^{3+}(0.1\mathrm{M})+3\mathrm{Ag}\left(\mathrm{s}\right)$

The ${\left(\frac{\partial \mathrm{E}}{\partial \mathrm{T}}\right)}_{\mathrm{P}}$ of different types of half cells are as follows :
$\begin{array}{cccc}\mathrm{A}& \mathrm{B}& \mathrm{C}& \mathrm{D}\\ 1\times {10}^{-4}& 2\times {10}^{-4}& 0.1\times {10}^{-4}& 0.2\times {10}^{-4}\end{array}$

(Where $\mathrm{E}$ is the electromotive force). Which of the above half cells would be preferred to be used as reference electrode

In which metal container, the aqueous solution of ${\mathrm{CuSO}}_4$ can be stored?

${\mathrm{E}}_{{\mathrm{Cu}}^{3+}/\mathrm{Cu}}^0=0.34 \mathrm{V}$

$E_{Fe/F{e}^{2+}}^0=0.44V,E_{Al/A^{3+}}^0=1.66V$

$E_{Ni/N^{2+}}^0=0.25V,E_{A{g}^{+}/Ag}^0=0.80V$