Question

The number of moles of $KMnO_4$ that will be needed to react with one mole of sulphite ion in acidic solution is

• A. 44656
• B. 44597
• C. 1
• D. 44625

Answer 1

Answer: (B)

44597

Answer 2

$2KMnO_4 + 3H_2SO_4 \rightarrow K_2 SO_4 + 2MnSO_4$
$+3H_2O + 5 [O]$
$[MnO^{-}_4 + 8H^+ + 5e^-\rightarrow Mn^{2+} + 4H_2O] \times 2$
$\frac {[SO_3^{2-} + H_2O \rightarrow SO_4^{2-} + 2H^+ + 2e^-] \times 5} {2MnO_4^{-} + 6H^+ + 5SO_3^{2-} \rightarrow 2Mn^{2+} + 5 SO _4^{2-} + 3H_2O}$
$5$ moles of sulphite ions react with
= $2$ moles of $MnO_4^-$
So, $1$ mole of sulphite ions react with
$= \frac {2}{5} \, moles \, of \, MnO_4^{-}$.