$Mn^{2+} +2e- \rightarrow Mn;\, E^o = -1.18\,V$
$2(Mn^{3+} +e^- \rightarrow Mn^{2+} )\,;\,E^o=+1.51\,V$
The $E^o$ for $3Mn^{2+} \rightarrow Mn+ 2Mn^{3+}$ will be :
(b) $\quad M n^{3+}+e \rightarrow M n^{2+} ; \quad E^{\circ}=-1.51 V ; \ldots(i i)$
Now multiplying equation $(i i)$ by two and subtracting from equation $(i)$
$3 M n^{2+} \rightarrow M n^{+}+2 M n^{3+}$
$E^{\circ}=E_{O_{X}}+E_{\mathrm{Red} .}=-1.18+(-1.51)=-2.69 \mathrm{V}$
$[-\text { ve value of } E M F(\text { i.e., } \Delta G=+v e)$$ \text { shows that the reaction is non-spontaneous }]$
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
| List-$I$ | List-$II$ | ||
| $A$ | $[Fe(H_2O)_6]^{2+}$ | $P$ | $0$ |
| $B$ | $[Fe(H_2O)_6]^{3+}$ | $Q$ | $1$ |
| $C$ | $[Fe(CN)_6]^{4-}$ | $R$ | $2$ |
| $D$ | $[Fe(CN)_6]^{3-}$ | $S$ | $4$ |
| $E$ | $[Ni(H_2O)_4]^{2+}$ | $T$ | $5$ |
$A$ $||$ $B$ $||$ $C$ $||$ $D$ $||$ $E$