The reaction which occur in the Galvanic cell is
             $\begin{array}{c}{\mathrm{MnO}}_4^{-}+8{\mathrm{H}}^{+}+5{\mathrm{Fe}}^{2+}⟶{\mathrm{Mn}}^{2+}+5{\mathrm{Fe}}^{3+}+4{\mathrm{H}}_2\mathrm{O}\\ {\mathrm{E}}^{\circ }\left({\mathrm{MnO}}_4^{-},{\mathrm{Mn}}^{2+},{\mathrm{H}}^{+}\mid \mathrm{Pt}\right)=1.51\mathrm{V}\text{ and }\\ {\mathrm{E}}^{\circ }\left({\mathrm{Fe}}^{3+},{\mathrm{Fe}}^{2+}\mid \mathrm{Pt}\right)=0.77\mathrm{V}\end{array}$
(Q) How would the emf of the cell be increased above the standard emf ?

• A

  By decreasing pH

• B

  By increasing $\left[{\mathrm{Fe}}^{3+}\right]$

• C

  By decreasing $\left[{\mathrm{MnO}}_4^{-}\right]$

• D

  By increasing $\left[{\mathrm{Mn}}^{2+}\right]$