Question

The number of moles of $KMn{O}_4$ that will be needed to react with $1$ mol of sulphite ion ($S{O}_3^{2-}$) in acidic solution is:

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

Answer 1

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

As we know,
Equivalents of $Mn{O}_4^{\ominus }=$ Equivalents of $S{O}_3^{2-}(S{O}_3^{2-}⟶S{O}_4^{2-}+2e^{-})$
$(n=5)$ $(n=2)$
$1$ Eq. $=$ $1$ Eq.
$\frac{1}{5}$ mol $=\frac{1}{2}$ mol
$\frac{2}{5}$ mol of $Mn{O}_4^{\ominus }=1$ mol of $S{O}_3^{2-}$