Chemistry - Electrochemistry Question with Solution | TestHub

$\mathrm{F}{\mathrm{e}}^{6+}+3\mathrm{e}\to \mathrm{F}{\mathrm{e}}^{3+};$$-\mathrm{\Delta }{\mathrm{G}}_1^{\mathrm{o}}=3\times 2.20\times \mathrm{F}$…(i)
$\mathrm{F}{\mathrm{e}}^{3+}+\mathrm{e}\to \mathrm{F}{\mathrm{e}}^{2+};$$-\mathrm{\Delta }{\mathrm{G}}_2^{\mathrm{o}}=1\times 0.77\times \mathrm{F}$…(ii)
$\mathrm{F}{\mathrm{e}}^{2+}+2\mathrm{e}\to \mathrm{F}{\mathrm{e}}^{\mathrm{o}};$$-\mathrm{\Delta }{\mathrm{G}}_3^{\mathrm{o}}=2\times (-0.445)\times \mathrm{F}$…(iii)
By equation (i) and (ii)
$\mathrm{F}{\mathrm{e}}^{6+}+4\mathrm{e}\to \mathrm{F}{\mathrm{e}}^{2+};$$-\mathrm{\Delta }{\mathrm{G}}_4^{\mathrm{o}}=-\mathrm{\Delta }{\mathrm{G}}_1^{\mathrm{o}}-\mathrm{\Delta }{\mathrm{G}}_2^{\mathrm{o}}$
Hence$4\times {\mathrm{E}}_4^{\mathrm{o}}\times \mathrm{F}=3\times 2.20\times \mathrm{F}+\left(1\times 0.77\times \mathrm{F}\right)$
So${\mathrm{E}}_4^{\mathrm{o}}=1.84\mathrm{V}$
or$\mathrm{F}{\mathrm{e}}^{6+}+4\mathrm{e}\to \mathrm{F}{\mathrm{e}}^{2+};$${\mathrm{E}}^{\mathrm{o}}=1.84\mathrm{V}$