Question

{KMnO}_{4}

acts as a strong oxidising agent in acidic, alkaline and neutral medium. Give one example of each.

Accepted Answer

${KMnO}_{4}$ is an important compound of Mn the member of the First Transition Series. The oxidation state of the Mn atom in ${KMnO}_{4}$ is $+ 7$ . It shows its highest oxidation state so, now it can change to its lower oxidation state only gain of electrons. ${KMnO}_{4}$ is reduced in acidic, basic as well as in neutral medium thus making it an excellent oxidising agent in these mediums.

Acidic medium-The compound behaves in an acidic medium as follows.

$2 {KMnO}_{4} + H_{2} {SO}_{4} \to K_{2} {SO}_{4} + 2 {MnSO}_{4} + 3 H_{2} O + 5 [O]$

${MnO}_{4} ¯ + 8 H^{+} + 5 e^{-} \to {Mn}^{2}^{+} + 4 H_{2} O$
${MnO}_{4} ¯ \to {Mn}^{2}^{+} Change in oxidation Number = 7 - 2 = + 5$

$Mn$ is reduced by gain of $5$ electrons thus, Making it an excellent oxidizing agent. For example:-

$1 {0 FeSO}_{4} + 2 {KMnO}_{4} + 8 H_{2} {SO}_{4} = 5 {Fe}_{2} {({SO}_{4})}_{3} + 2 {MnSO}_{4} + K_{2} {SO}_{4} + 8 H_{2} O$

Basic medium-The compound behaves in a basic medium as follows.

${KMnO}_{4} + KOH \to K_{2} {MnO}_{4} + H_{2} O + O$

${MnO}_{4} ¯ + e^{-} \to {MnO}_{4}^{2}^{-}$

$Change in oxidation Number = 7 - 6 = + 1$

$Mn$ is reduced by gain of $1$ electron thus, Making it a much weaker oxidizing agent. For example:- $2 {KMnO}_{4} + H_{2} O + KI \to 2 {MnO}_{2} + 2 KOH + {KIO}_{3} $

Neutral medium- The compound behaves in a neutral medium as follows.

$2 {KMnO}_{4} + H_{2} O \to 2 {MnO}_{2} + 2 KOH + 3 O$

$2 H_{2} O + {MnO}^{4 -} + 3 e - \to {MnO}_{2} + 4 {OH}^{-} Change in oxidation Number = 7 - 4 = + 3$

$Mn$ is reduced by gain of $4$ electrons thus, making it good oxidising reagent.

example: $8 MnO 4^{-} + 3 S_{2} {O_{3}}^{2 -} + H_{2} O \to 8 MnO 2 + 6 {SO}_{4}^{2 -} + 2 {OH}^{-}$

Thus, you can see that oxidizing effect of ${KMnO}_{4}$ is maximum in acidic medium and least in basic medium as in acidic medium the reduction in oxidation state of Mn is max while it is the least in basic medium.

Hence, acidic medium is used when you want strong oxidization and basic when very mild oxidization is required.

${KMnO}_{4}$ acts as a strong oxidising agent in acidic, alkaline and neutral medium. Give one example of each.

Important Questions on d- and f-Block Elements

Learn and Prepare for any exam you want !

KMnO4 acts as a strong oxidising agent in acidic, alkaline and neutral medium. Give one example of each.

Important Questions on d- and f-Block Elements

Learn and Prepare for any exam you want !

${KMnO}_{4}$ acts as a strong oxidising agent in acidic, alkaline and neutral medium. Give one example of each.