Question

Identify oxidant and reductant in the following redox reactions.
$2Mn{O_4}^{ - 2} + 2{H_2}O\xrightarrow{{current}}2Mn{O_4}^ - + 2O{H^ - } + {H_2}$
(A) Oxidant:${H_2}O$; Reductant:$Mn{O_4}^{ - 2}$
(B) Oxidant:${H_2}O$ Reductant:${H_2}$
(C) Oxidant: $Mn{O_4}^{ - 2}$ Reductant:${H_2}O$
(D) None of these

Answer 1

In this question we will put light on the topic of redox reaction, oxidation, reduction, reducing agent and oxidising agent. We will study the terms oxidant and reductant and all the related information. After knowing them we can easily solve this question. Below here we have discussed each and every concept thoroughly.

Complete step-by-step answer:

Redox Reaction: There are many reactions occurring in our daily life. The classical example of redox is rusting. Redox reactions name is derived from two-word oxidation and reduction, which itself clarifies the fact and meaning of redox reaction. In this reaction when oxidation occurs at the same time reduction will also take place.
Oxidation: oxidation involves:
i) Addition of oxygen or addition of electronegative elements.
ii) Removal of hydrogen or removal of electropositive elements.
To summarise, the term oxidation we can say it is defined as the coming of oxygen/electronegative element to a substance or removal of hydrogen/ electropositive element from a substance.
- Oxidising Agent or Oxidant: A substance which supplies oxygen or any other electronegative elements or removes hydrogen or any other electropositive element
Reduction: Reduction involves:
i) Addition of hydrogen or addition of electropositive element.
ii) Removal of oxygen or removal of electronegative elements.
To summarise, the term reduction we can say is defined as the coming of hydrogen/electropositive element to a substance or removal of oxygen/ electronegative element from a substance.
- Reducing Agent or Reductant: A substance which has hydrogen to give to any other electropositive elements or removes oxygen or any other electropositive element.
$2Mn{O_4}^{ - 2} + 2{H_2}O\xrightarrow{{current}}2Mn{O_4}^ - + 2O{H^ - } + {H_2}$
Here, as we can see
The oxidation state of H decreases from $+ 1\,to\,0$ which shows that hydrogen is reduced.
The oxidant is ${H_2}O$ the oxidation state of Mn rises from $+ 6\,to\, + 7$ . Which shows that Mn is oxidized.
The reductant is $Mn{O_4}^{ - 2}$
Hence, the correct answer is option (A).

Note: Redox reactions can be defined as the reactions in which the oxidation states of the atoms are changed as the electron transfer takes place. All redox reactions are based on the partial or complete transfer of the electrons from one atom to the other atom. For example, the production of vegetable ghee is a redox reaction. Also, the information that we have studied in this question will help us in solving these kinds of questions.