Question

In the reaction between ethylene and alkaline $KMn{O}_4$, the oxidation number of manganese ___________.

• A. decreases from $+7$ to $+2$
• B. decreases from $+7$ to $+6$
• C. decreases from $+7$ to $+4$
• D. increases from $+4$ to $+7$

Answer 1

The correct option is C decreases from $+7$ to $+4$

In alkaline conditions: $Mn{O}_4^{-}⟶Mn{O}_2$

In $Mn{O}_4^{-}$, oxidation number of Mn is $+7$.

In $Mn{O}_2$ ,oxidation number of Mn is $+4$.

Hence, it changes from $+7$ to $+4$.