Question

The number of moles of $KMn{O}_4$ that will be needed to react with one mole of sulphite ion in acidic solution is:

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

Answer 1

The correct option is D

$\frac{2}{5}$

$\stackrel{+7}{2Mn{O}_4^{-}}+5S{O}_3^{2-}+6H^{+}\to 5S{O}_4^{2-}+\stackrel{+2}{2M{n}^{+2}}+3H_{2}O$

Since 2 miles of manganate are needed to oxidize 5 moles of sulphite anion:

$\Rightarrow$ Number of moles of $KMn{O}_4$ that react with one mole $S{O}_3^{2-}$ will be $\frac{2}{5}$