Question

How do you identify the oxidizing agent in the following chemical reaction?
$2Mn{O^ - }_4 + 5{H_2}S{O_3} \to M{n^{2 + }} + 5S{O^{2 - }}_4 + 4{H^ + } + 3{H_2}O$

Answer 1

In order to find the oxidizing agent from a reaction we must know the exact meaning of an oxidizing agent. An oxidizing agent is the one whose oxidation number decreases during the redox process. We can also say that the oxidising agent or which is also called the oxidiser is a substance which has the ability to oxidize other substances or has the ability to accept their electrons. Common examples of oxidizing agents are oxygen, hydrogen peroxide and the halogens.

Complete answer:
The chemical reaction from which we have to find the oxidizing agent is as follows,
$2Mn{O^ - }_4 + 5{H_2}S{O_3} \to M{n^{2 + }} + 5S{O^{2 - }}_4 + 4{H^ + } + 3{H_2}O$
In this reaction, the deep purple color is lost at the endpoint. Because of this color change, this redox reaction is said to be self-indicating.
In the above reaction sulfite is oxidized to sulfate and hence it acts as a reducing agent.
Whereas manganese which is present as permanganate is reduced to nearly colorless $M{n^{2 + }}$ .
Hence, we can say that permanganate ion is the oxidizing agent here.

Note: The oxidizing agent is also called an electron acceptor and the reducing agent is called an electron donor. The dangerous goods definition of an oxidizing agent is a substance that can cause or contribute to the combustion of other material. Hence we can say that some materials that are classified as oxidizing agents by analytical chemists are not classified as oxidizing agents in a dangerous materials sense. An example is potassium dichromate, which does not pass the dangerous goods test of an oxidizing agent.