Question

A given amount of ${Fe}^{2+}$ is oxidised by $x$ moles of $Mn{O}_4^{-}$ in acidic medium. Calculate number of moles of ${Cr}_2{O}_7^{2-}$ required to oxidise same amount in ${Fe}^{2+}$ in acidic medium if $x=5$.

• A. 6
• B. 5.4
• C. 7
• D. None of these

Answer 1

The correct option is A 6

The balanced reactions are as follows:
$6{Fe}^{2+}+{Cr}_2{O}_7^{2-}\underset{}{\overset{H^{+}}{\to }}2{Cr}^{3+}+H_{2}O+6{Fe}^{3+}$
$5{Fe}^{2+}+Mn{O}_4^{-}\underset{}{\overset{H^{+}}{\to }}{Mn}^{2+}+H_{2}O+5{Fe}^{3+}$
$\frac{MoleofMn{O}_4^{-}}{Moleof{Cr}_2{O}_7^{2-}}=\frac{5}{6}\left(ratioof{Fe}^{2+}oxidised\right)$
$\Rightarrow Moleof{Cr}_2{O}_7^{2-}=1.2x$