Chapter 8

Redox Reactions

As we all know that Science is incomplete without Chemistry. It gives life and soul to Science. It explains all the reactions and molecules in the environment, right from a tiny atom to everything else. Redox Reactions form a significant part of this that tries to explain the oxidation and reduction reactions that take place in the environment around us. 

Often students try to surpass this chapter, making it difficult to find the NCERT Solutions for Class 11 Chemistry Chapter 8. However, to clear your doubts, Redox Reactions is one of the most important chapters of Class 11 Chemistry. Several questions are asked from Class 11 Redox Reactions every year. Moreover, the redox reactions also find a special place in Biology and will help you understand many terms in that subject as well. 

We have created a list of all the important and frequently asked terms from the Class 11 Chemistry Redox Reactions chapter for your convenience. In this way, you'll have deep insight into all the simple as well as complicated terms included in this chapter. That will help you find Redox Reactions Class 11 NCERT Solutions. As you may already know, most of the questions are directly asked out of your NCERT textbook, makings the Class 11 Chemistry Chapter 8 NCERT solutions all the more important.

Let's have a step-by-step look at all the important and noteworthy terms of this chapter.

Topics Covered in This Chapter: Content Table

 

S. No

Topics

1. 

Introduction

2. 

Classical Idea of Redox Reactions

3. 

Redox Reaction in Terms of Electron Transfer Reaction 

4. 

Oxidation Number

5. 

Redox Reaction and Electrode Process

6. 

FAQs 

 

Introduction

Before we get into all the details of the Class 11 Redox Reactions, we must understand the basics of the same. Before our foundation is strong, we can't build anything over it. Henceforth, let's understand the simple terms known as redox reactions. 

What are redox reactions? 

As the name suggests, redox reactions can be broken down into two: reduction and oxidation. Any reaction where both the processes take place simultaneously is known as a redox reaction. It also means that this reaction involves the gain or loss of electrons concerned with the oxidation and reduction processes. 

In this chapter, we will deal with all the concepts related to Redox Reactions in a simple or complicated way. Redox Reactions are the most common type of reactions that take place in the environment every day. That's why it is so important to familiarise yourself with all the concepts that come under this chapter.

A redox reaction is made of two equally important parts. They are:

  • Oxidation Reaction
  • Reduction Reaction

Let's talk about these two terms in-depth.

  • Oxidation Reaction
    Any reaction where the element oxygen is added to the reaction is known as oxidation. It also means that an electronegative element i.e., Oxygen, is being added to the reactants, and removing Hydrogen or an electropositive element takes place. Hence, oxygen is added, and hydrogen is removed from the reaction. This is oxidation in a nutshell.

    For instance,

  • Reduction Reaction
    Any reaction wherein the element hydrogen is added to the reaction is known as a reduction reaction. It also means that an electropositive element (Hydrogen) is added to the reaction, and an electronegative element (Oxygen) is removed from the reaction. It is known as reduction. It is the opposite of an oxidation reaction.
     
    For instance,  

There are various types of redox reactions. Some of them are:

  • Combination Reaction
    It is a reaction when two or more substances combine to form a new substance. It is called a combination reaction or synthesis reaction.
    The general representation of a combination reaction is:
    A + B ---> C 

  • Decomposition Reaction
    It is the reciprocal of a combination reaction. In this reaction, a compound breaks down into two or simpler compounds. It is called a decomposition reaction.
    A simple representation would be:
    AB ---> A + B 

  • Displacement Reaction
    In this type of reaction, a more reactive element goes on to displace a less reactive element.
    It can be represented by:
    AB + C ----> CB + A

  • Disproportionate Reaction
    In this type of reaction, a single element goes through both oxidation and reduction. A single reactant goes through the same. 2H2O2 -----> 2H2O + O2

According to the electronic concept, every redox reaction is completed in two steps known as half-reactions.

  • Oxidation Reactions
    These reactions involve the loss of electrons. 
  • Reduction Reaction
    These reactions involve the gain of electrons.

Now, if we look further:

  • Oxidising Agent: Any element or compound that undergoes reduction is known as an oxidising agent. It is the acceptor of electrons. 
  • Reducing Agent: Any element or compound that undergoes oxidation is known as a reducing agent. It is the donor of electrons.

It is defined as the individual charge present on one atom when all the other atoms are completely removed. 

The important points that help in determining the oxidation number of any element are:

  • Any atom in its pure elemental form does not have any oxidation number. It is considered zero. For instance, Na, Mg have 0 as their oxidation number. 
  • The oxidation number of fluorine is -1 with any other elements whenever it forms a compound. 
  • The oxidation number of a monatomic ion equals the charge on that ion. For instance, Na will have a charge of +1. 
  • Oxygen always shows an oxidation number of -2. However, it shows -1 with hydrogen peroxide and +2 with OF2. 
  • Halogens always show their oxidation number as -1 when they form bonds with electronegative elements. 
  • Alkali metals like Na, K have an oxidation number of -1. Whereas alkali earth metals like Ca and Mg are +2. 
  • The sum of the oxidation number of all the atoms is a neutral compound will always equal 0. In the case of an ion, the oxidation number represents the charge on it. 
  • If a compound has two non-metallic atoms, the atoms with more electronegativity will have negative oxidation numbers, whereas electro-positive atoms will possess electro-positive oxidation numbers.

Fractional Oxidation Numbers

There is no presence of fractional oxidation numbers as such. However, when the same element is involved in bonding with different species, the average oxidation number can be fractional.

For example,

It can be calculated after knowing the structure and bond position well.

Balancing of Redox Reactions

(i) By using the oxidation number method 

It can be done by the following steps:

  • Write the correct equation with the reactants and products. 
  • By looking at the oxidation change, identify the oxidation number and take note. 
  • Calculate the oxidation number by multiplying with the coefficient present. 
  • Balance the equation by keeping all the atoms in mind. 
  • If the reaction is in an acidic medium, add H+ ions and if it's basic, use OH- ions. 
  • If you want to balance the Hydrogen atoms in the expression, add water molecules to the respective products or reactants side.

(ii) By using Half Reaction Method 

For this method, two half-reactions are considered. Then, they are balanced separately. Then they can be added together to yield a balanced reaction.

Electrochemical Cell: A device where a redox reaction is carried out indirectly so that the decrease in energy is yielded as the electrical energy is known as an electrochemical cell. 

Electrolytic Cell: In this cell, electrical energy changes into chemical energy.

In a copper sulphate solution, a zinc rod is dipped. A redox reaction starts taking place here. We see that zinc is oxidised to Zn2+ ions. On the other hand, Copper is reduced to metal which was initially Cu2+ ions.

1. What is meant by redox reaction?

A reaction wherein both oxidation and reduction processes take place simultaneously is known as a redox reaction.

2. List out the important topics covered in this chapter.

Many topics are covered in this chapter. They are redox reaction introduction, oxidation, reduction, a redox reaction in terms of electron transfer, oxidation number, and electrode processes.

3. What is an Oxidation Number? 

It is simply the oxidation state of an element in any compound. In simple words, it is the charge obtained by gaining or losing electrons.

 

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