Chemistry - Electrochemistry Question with Solution | TestHub

$\Delta {\text{G}}^{\circ }=-\text{nF}{\text{E}}^{\circ }$

${\text{Mn}}^{+2}+2{\text{e}}^{-}\to \text{Mn}$........... (1)

$\Delta \text{G}=-2\times \text{F}\times \left(-\text{1.18}\right)=+\text{2.36 F}$

$2{\text{Mn}}^{+3}+2{\text{e}}^{-}\to 2{\text{Mn}}^{+2}$....... (2)

$\Delta \text{G}=-2\times \text{F}\times \left(\text{+1.51}\right)=-\text{3.02 F}$

(1) - (2)

$3{\text{Mn}}^{+2}\to \text{Mn}+2{\text{Mn}}^{+3}$

$\Delta \text{G}=+\text{2.36F}+\left( \text{3.02F}\right)=\text{5.38 F}$

$\Delta \text{G}=-2\times \text{F}\times \text{E}$

$\text{E}=\frac{\text{5.38F}}{-2\times \text{F}}=-\text{2.69 V}$

We know that when E_cell< 0, cell is non-spontaneous.