$0.01$ moles of electrons are passed through three cells connected in series, each containing aqueous solutions of $\mathrm{KCl}, {\mathrm{AgNO}}_3$ and ${\mathrm{H}}_2{\mathrm{SO}}_4$. The total volume of hydrogen evolved in the set-up at STP is

For hydrogen-oxygen fuel cell, the cell reaction is

$2{\mathrm{H}}_2 \left(\mathrm{g}\right)+{\mathrm{O}}_2 \left(\mathrm{g}\right)⟶2{\mathrm{H}}_2\mathrm{O} \left(\mathrm{\ell }\right)$

If ${{\mathrm{\Delta G}}^{°}}_{\mathrm{f}}\left({\mathrm{H}}_2\mathrm{O}\right)=-237.2 \mathrm{kJ} {\mathrm{mol}}^{-1},$ the emf of this cell is

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

$\mathrm{E}°=1.51 \mathrm{V}$

${\mathrm{MnO}}_2+4{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}⟶{\mathrm{Mn}}^{2+}+2{\mathrm{H}}_2\mathrm{O}$

$\mathrm{E}°=1.23 \mathrm{V}$

${{\mathrm{E}}^{\circ }}_{{{\mathrm{MnO}}_4}^{-}/{\mathrm{Mno}}_2}$ is