Question

The oxidizing agent in the following reaction is:
$2Mn{O_4}^ - + {\text{ }}16{H^ + } + {\text{ }}5{C_2}{O_4}^{2 - } \to 2M{n^{2 + }} + {\text{ }}8{H_2}O{\text{ }} + {\text{ }}10C{O_2}$
A.$Mn{O_4}^ -$
B.${H^ + }$
C.${C_2}{O_4}^{2 - }$
D.Both $Mn{O_4}^ -$and ${H^ + }$

Answer 1

Oxidation is the process in which a species loses electrons and reduction is the process in which species gains electrons. In oxidation generally, the positive oxidation state increases and in reduction it decreases. Oxidizing agent is the species which makes the other species oxidize i.e. which accepts electrons from others (itself gets reduced).

Complete step-by-step answer: When a reaction occurs, either there is gain of electrons or loose of electrons so this exchange of electrons takes place and which finally leads to formation of products. In redox chemistry, there occurs a process called Oxidation and reduction. So, oxidation is the process which involves loss of electrons and reduction is the process in which gain of electrons takes place.
So, if a substance is losing out electrons then it is said that it is undergoing oxidation.
Oxidizing agent is the substance which makes other substances undergo oxidation i.e. itself get reduced. So, in the given reaction in the question, we will look at the species which is accepting electrons and going under reduction.
That species will be called an oxidizing agent.
This could be done out by calculating oxidation number and how it is changing in the reaction.
So, Oxidation state of $Mn$in $Mn{O_4}^ -$
$\Rightarrow x - 4\left( { - 2} \right){\text{ }} = {\text{ }} - 1$
$\Rightarrow x = + 7$
Oxidation state of $Mn$in product = $+ 2$
Similarly, oxidation state of $C$ in ${C_2}{O_4}^{2 - }$
$\Rightarrow 2x - 4\left( { - 2} \right){\text{ }} = {\text{ }} - 2$
$\Rightarrow x = + 3$
Oxidation state of $C$in product i.e. $C{O_2}$
$\Rightarrow x - 2\left( { - 2} \right){\text{ }} = {\text{ }}0$
$\Rightarrow x{\text{ }} = {\text{ }} + 4$
So, we see that $Mn$is the one which is accepting electrons and carbon is the one which is losing electrons.
So, the species which is oxidizing agent i.e. getting reduced itself is $Mn{O_4}^ -$

Hence, the answer is A i.e. $Mn{O_4}^ -$.

Note: A redox reaction or oxidation-reduction reaction is the one which involves both processes simultaneously and transfer of electrons from one species to another. To identify such types of reactions and reduce agents and oxidizing, it could be done easily by firstly calculating oxidation state and then looking at how its changing during the reaction.