Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diph

Question

Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is\

Professor PC Thomas Classes · Answer

(d) : In the redox reaction, $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$ oxidises Mohr's salt,\ $\mathrm{FeSO}_{4} \cdot\left(\mathrm{NH}_{4}ight)_{2} \mathrm{SO}_{4} \cdot 6 \mathrm{H}_{2} \mathrm{O} \cdot 6 \mathrm{Fe}^{2+}+\mathrm{Cr}_{2} \mathrm{O}_{7}{ }^{2-}$ $$ +14 \mathrm{H}^{+} ightarrow 6 \mathrm{Fe}^{3+}+2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O} $$ Mohr's salt $\left[\mathrm{FeSO}_{4} \cdot\left(\mathrm{NH}_{4}ight)_{2} \mathrm{SO}_{4} \cdot 6 \mathrm{H}_{2} \mathrm{O}ight.$ ] and dichromate reacts in $6: 1$ molar ratio. Or one mole of $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$ will require six moles of $\mathrm{Fe}^{2+}$ ions.\