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 in each case respectively are:

• A. $1,3,4,5$
• B. $3,2,1,4$
• C. $1,5,3,7$
• D. $4,3,2,1$

Answer 1

Answer: (A)

$1,3,4,5$

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 in each case are 1,3,4,5 respectively.

The oxidation number of Mn in $KMn{O}_4$, $Mn{O}_4^{2-},Mn{O}_2,M{n}_2{O}_3$ and $M{n}^{2+}$ is 7, 6, 4, 3 and 2 respectively.

The number of electrons transferred corresponds to the change in the oxidation number.
For example, when $KMn{O}_4$ forms $Mn{O}_4^{2-}$, the change in the oxidation number is $7-6=1$. Hence, the number of electrons transferred is 1.