Question

$KMn{O}_4$ acts as an oxidising agent in an acidic medium. The number of moles of $KMn{O}_4$ that will be needed to react with one mole of sulphide ions in an acidic solution is:

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

Answer 1

The correct option is B $\frac{2}{5}$

The balanced chemical reaction between $KMn{O}_4$ and sulphide ion in an acidic medium is shown below.
$\begin{array}{c}5S^{2-}+2Mn{O}_4^{-}+16H^{+}\stackrel{Acidicmedium}{\to }\\ 2M{n}^{2+}+8H_{2}O+5S\end{array}$

According to the reaction,

$5mol$ of $S^{2-}$ reacts with $\to$$2mol$ of $KMn{O}_4.$

Thus, $1mol$ of $S^{2-}$ will react with $\to$ $\frac{2}{5}mol$ of $KMn{O}_4.$

Thus, the number of moles of $KMn{O}_4$ that will be need to react with one mole of sulphide ions in acidic solution is $\frac{2}{5}$

So, option $\left(A\right)$ is the correct answer.