The quantity of electricity in Faraday needed to reduce 1 mol of ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ to ${\mathrm{Cr}}^{3+}$ is _________.

$\underset{1 \mathrm{mol}}{{\mathrm{Cr}}_2{\mathrm{O}}_7^{-2}}+\underset{6 \mathrm{mol}}{6{\mathrm{e}}^{-}}⟶2{\mathrm{Cr}}^{+3}$
Number of faradays = moles of electrons, as the respective conversion need 6 mole of electrons, therefore 6 F is required.