Question

The number of moles of $KMn{O}_4$ that will be needed to react completely with one mole of ferrous oxalate in acidic medium is

• A. $\frac{2}{5}$
• B. $\frac{3}{5}$
• C. $\frac{4}{5}$
• D. 1

Answer 1

Answer: (B)

The number of moles of $KMn{O}_4$ that will be needed to react completely with one mole of ferrous oxalate in acidic solution is $\frac{3}{5}$.
Potassium permangante is a very strong oxidizing agent. It oxidizes iron(II) ion as well as the oxalate ion.
Oxalate oxidation: $2Mn{O}_4-+16H^{+}+5C_2{O}_4^{2-}\to 2M{n}^{2+}+8H_{2}O+10C{O}_2$
Iron(II) oxidation: $Mn{O}_4^{-}+8H^{+}+5F{e}^{2+}\to M{n}^{2+}+4H_{2}O+5F{e}^{3+}$
Hence, moles of $KMn{O}_4$ that will be needed to react completely with one mole of ferrour oxalate $Fe\left(C_2{O}_4\right)$ is $\frac{3}{5}$ ($2$ moles for oxalate and $1$ mole for iron (II)).