Question

Aqueous sulphite reacts with dilute sulphuric acid to form $X(g)$. The liberated $X(g)$ is oassed into acidified $KMnO _{4}$ solution. What s the oxidation state of $Mn$ in the product formed?

• A. +6
• B. +4
• C. +2
• D. +3

Answer 1

Answer: (C)

Aqueous sulphite when reacts with sulphuric acid, it gives $SO _{2}(g)$ which when react (passed) with acidified $KMnO _{4}$ gives $Mn ^{2+}$ ions as follows:

(i) $SO _{3}^{2-}+ H _{2} SO _{4} \longrightarrow SO _{4}^{2-}+ SO _{2}+ H _{2} O$

(ii) $5 SO _{2}+2 KMnO _{4}+2 H _{2} O \longrightarrow K _{2} SO _{4}$

$+2 MnSO _{4}+2 H _{2} SO _{4}$

$\because$ Oxidation state of $Mn$ in $MnSO _{4}$ is $+2$