Question

When $KMn{O_4}$ reacts with acidified $FeS{O_4}$ ______.
A. Only $FeS{O_4}$ is oxidized.
B. Only $KMn{O_4}$ is oxidized.
C. $FeS{O_4}$ is oxidized and $KMn{O_4}$ is reduced.
D. $KMn{O_4}$ and $FeS{O_4}$ oxidized.

Answer 1

Hint: The chemical reactions in which one species is reduced and other is oxidized in a single reaction simultaneously is known as redox reaction. When an atom gains an electron and reduction in the oxidation number is observed then it is said to be reduced whereas if an atom loses an electron and the oxidation number increases, then it is said to be oxidation. The reaction of $KMn{O_4}$ with acidified $FeS{O_4}$ is an example of a redox reaction.

Complete answer:
In ferrous sulphate, the oxidation state of iron is +2 and in potassium permanganate, the oxidation state of manganese is +7 and, in the reaction, acidified ferrous sulphate indicates the presence of acidic medium i.e., sulphuric acid. That means $KMn{O_4}$ reacts with $FeS{O_4}$ in the presence of ${H_2}S{O_4}$ to produce ferric sulphates, manganese sulphates, potassium sulphates and water. The basic mechanism followed during the reaction involved oxidation reduction.
Half reactions involved during the redox reaction are as follows:
Oxidation half reaction:
Iron on reaction with potassium permanganate loses its electron and its oxidation state changes from +2 to +3 as follows:
$F{e^{ + 2}} \to F{e^{ + 3}} + {e^ - }$
Reduction half reaction:
In the reaction, manganese accepts five electrons and it get reduced to its +2-oxidation state as follows:
$MnO_4^ - + 8{H^ + } + 5{e^ - } \to M{n^{2 + }} + 4{H_2}O$
Thus, we can conclude that when $KMn{O_4}$ reacts with acidified $FeS{O_4}$, $FeS{O_4}$ is oxidized and $KMn{O_4}$ is reduced.
Hence, option (C) is the correct answer.

Note:
It is important to note that potassium permanganate is used in many chemical reactions because of its tendency to behave as good oxidizing agent because the central metal i.eManganese is present at its highest oxidation state which means it can readily accepts electrons to get self-reduced and oxidized other compounds.