What is $\Delta G^{\circ}$ per mole of dichromate ions for the reduction of $\mathrm{Cr}_2 \mathrm{O

Question

What is $\Delta G^{\circ}$ per mole of dichromate ions for the reduction of $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ to $\mathrm{Cr}^{3+}$ by bromide ions, in acidic solution?
Given $\mathrm{E}_0 \mathrm{Cr}_2 \mathrm{O}_7^{2-} / \mathrm{Cr}^{3+}=1.33, \mathrm{Br}_2 / \mathrm{Br}-$ =1.01V

Professor PC Thomas Classes · Answer

$\mathrm{Cr}_{2} \mathrm{O}_{7^{2-}}+6 \mathrm{Br}^{-}+14 \mathrm{H}^{+} ightarrow$ $$ 2 \mathrm{Cr}^{3+}+3 \mathrm{Br}_{2}+7 \mathrm{H}_{2} \mathrm{O} $$ $\mathrm{E}_{0}$ for cell reaction is $\left.1.33-1.01ight)=0.23 \mathrm{~V}$\ $\Delta \mathrm{G}^{\mathrm{o}}=-\mathrm{nF} \mathrm{E}_{0}=-6 	imes 96500 	imes 0.23=-133 \mathrm{~kJ}$\