Question

When $KMn{O}_4$ acts as an oxidising agent and ultimately forms $Mn{O}_4^{2-}$,$Mn{O}_2$, $M{n}_2{O}_3$ and $M{n}^{2+}$, then the number of electrons transferred per molecule of $KMn{O}_4$ in each case respectively, is:

• A. 4, 3, 1, 5
• B. 1, 5, 3, 7
• C. 1, 3, 4, 5
• D. 3, 5, 7, 1

Answer 1

The correct option is C 1, 3, 4, 5

Change in oxidation of Mn as the reactions are given below:
$\stackrel{+7}{Mn}{O}_4^{-}+e\to \stackrel{+6}{Mn}{O}_4^{2-}$ ; Change in oxidation is 1
$\stackrel{+7}{Mn}{O}_4^{-}+3e\to \stackrel{+4}{Mn}{O}_2$ ; Change in oxidation is 3
$\stackrel{+7}{Mn}{O}_4^{-}+4e\to {\stackrel{+3}{Mn}}_2{O}_3$ ; Change in oxidation is 4
$\stackrel{+7}{Mn}{O}_4^{-}+5e\to \stackrel{+2}{Mn}$ ; Change in oxidation is 5
Hence, the change is 1, 3, 4, 5 respectively.