Question

13. Define oxidizing agent and reducing agent with examples.
C​

Answer 1

Oxidizing and reducing agents are key terms used in describing the reactants in redox reactions that transfer electrons between reactants to form products. This page discusses what defines an oxidizing or reducing agent, how to determine an oxidizing and reducing agent in a chemical reaction, and the importance of this concept in real world applications.

Oxidizing and Reducing Agents

An oxidizing agent, or oxidant, gains electrons and is reduced in a chemical reaction. Also known as the electron acceptor, the oxidizing agent is normally in one of its higher possible oxidation states because it will gain electrons and be reduced. Examples of oxidizing agents include halogens, potassium nitrate, and nitric acid.

A reducing agent, or reductant, loses electrons and is oxidized in a chemical reaction. A reducing agent is typically in one of its lower possible oxidation states, and is known as the electron donor. A reducing agent is oxidized, because it loses electrons in the redox reaction. Examples of reducing agents include the earth metals, formic acid, and sulfite compounds.



Definitions

A reducing agent reduces other substances and loses electrons; therefore, its oxidation state increases.

An oxidizing agent oxidizes other substances and gains electrons; therefore, its oxidation state decreases

Table 1: Commons oxidizing and reducing agents

Common oxidizing agents

Common reducing agents

O2

H2

O3

CO

F2

Fe

Br2

Zn

H2SO4

Li

Halogens (they favor gaining an electron to obtain a noble gas configuration)

Alkali metals (they favor losing an electron to obtain a noble gas configuration)

To help eliminate confusion, there is a mnemonic device to help determine oxidizing and reducing agents.

OIL RIG:

Oxidation Is Loss and Reduction Is Gain of electrons

Example 1: Identify reducing and oxidizing agents

Identify the reducing and oxidizing agents in the balanced redox reaction:

Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br2(aq)(1)(1)Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br2(aq)Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br2(aq)(1)

Oxidation half reaction

2Br−(aq)→Br2(aq)(2)(2)2Br−(aq)→Br2(aq)

Oxidation States: -1 0

Reduction Half Reaction

Cl2(aq)→2Cl−(aq)(3)(3)Cl2(aq)→2Cl−(aq)

Oxidation States: 0 -1

Overview

B- loses an electron; it is oxidized from Br- to Br2; thus, Br- is the reducing agent.

Cl2 gains one electron; it is reduced from Cl2 to 2 Cl-; thus, Cl2 is the oxidizing agent.

Exercise

Identify the oxidizing agent and the reducing agent in the following redox reaction:

MnO−4+SO2−3→Mn+2+SO2−4(4)(4)MnO4−+SO32−→Mn+2+SO42−

Solution

SS is the reducing agent and 

Answer 2

Answer:

(i) Oxidising agent: A substance which increases the oxidation number of an element.in a given substance and itself undergoes a decrease in oxidation number of a constituent element is called an oxidising agent.

(ii) Reducing agent: A substance which decreases the oxidation number of an element in a given substance and itself undergoes an increase in the oxidation number of a constituent element in it is called a reducing agent