$C{r_2}O_7^{2 - }\, + \,6{e^ - }\, + \,14{H^ + }\, \to 2C{r^{3 + }}\, + \,7{H_2}O$
Oxidation half reaction :
$Cr\, \to \,C{r^{3 + }}\, + \,3{e^ - }$
Overall reaction :
$C{r_2}O_7^{2 - }\, + \,Cr\, + \,14{H^ + }\, + \,$ $3{e^ - }\, \to 3C{r^{3 + }}\, + \,7{H_2}O$
$3\,F$ of electricity $=\,3\,moles$ of $Cr^{3+}$
$1\,F$ of electricity $=\,\frac {3}{3}\,moles$ of $Cr^{3+}$
[આપેલ : $1\,F =96500\,C\,mol ^{-1},$ $Fe$નું પરમાણ્વીય દળ $= 56\,g\,mol ^{-1}$ ]
$[\Lambda_{\mathrm{H}^{+}}^{\circ}=350 \,\mathrm{~S}\, \mathrm{~cm}^{2}\, \mathrm{~mol}^{-1},\Lambda_{\mathrm{CH}_{3} \mathrm{COO}^{-}}^{\circ}=50\, \mathrm{~S}\, \mathrm{~cm}^{2}\, \mathrm{~mol}^{-1}]$
$\left[\right.$ આપેલ : $K _{ sp }( AgBr )=4.9 \times 10^{-13}$ at $298 K$
$\lambda_{ Ag ^{+}}^0=6 \times 10^{-3} Sm ^2\,mol ^{-1}$
$\lambda_{ Br ^{-}}^0=8 \times 10^{-3} Sm ^2\,mol ^{-1}$
$\left.\lambda_{ NO _3^{-}}^0=7 \times 10^{-3} Sm ^2\,mol ^{-1}\right]$