Class 11 Redox Reaction-Notes

NCERT  Class11 Chemistry  CHAPTER -8 

          REDOX REACTION

Notes 

Ch-8

In this chapter we will study about redox reactions that you have already learned in class10 So Now we will study in deep about redox reactions. 

What is Redox Reaction? 

We have already learned that Redox reactions in which oxidation is a gain Oxygen and Reduction is loss of oxygen is known as Redox reactions. 

But standard definition of Redox Reaction

That is

# Redox Reaction- All oxidation and reduction reactions are simultaneously takes place called Redox reactions. 

If we have equation of the reaction

Example:

C+O2==>CO2

there is Oxidation of the element that is C

and reduction of the element that is O2. 

Oxidising agent is O2 

Reducing agent is C

 

Oxidising agent- The substance which oxidises a other substances and gets reduced is called oxidising agent. 

Reducing agent- The substance which reduces a other substances and gets oxidised is called Reducing agent. 

Oxidation Number/State

It is defined as the charge that would be real or imaginery appears to have in the compound of that element is known as Oxidation state or oxidation number. 

# Rules for Assigning oxidation state/number

1) Oxidation state/number of Fluorine is always -1. 

2) Oxidation state/number of alkali metals always +1.

3) Oxidation state/number of the alkaline earth metals have always +2.

4) Oxidation state/number of oxygen always 90% is -2, but in peroxide is -1 and in superoxide is -1/2.

Peroxide H2O2

5) Oxidation state/number of the free or combined element in their independent states is zero

To find oxidation state/oxidation number

First Let take a example to find oxidation state/number of any element

Example:

1) SO2

To find oxidation state of S in SO2

• let oxidation state of S is x

Here the whole charge on the compound is zero

1*x+2(-2) =0

Because Oxygen is always charge is -2 

x=4

Therefore oxidation state/number of S in SO2 is +4

Note:Oxidation state/number of Sulphur is minimum -2 and maximum oxidation state/number is +6

Minimum oxidation state/number of Oxygen is -2 and Maximum oxidation state/number is +2.

TYPES OF REDOX REACTIONS

1) Combination Reaction

2) Decomposition Reaction

3) Displacement Reaction

4) Disproportionation Reaction-The reaction in which single element is oxidised as well as reduced in a single reaction is called Disproportionation Reaction. 

To Balancing of Redox Reactions

 1) By oxidation number

2) By electron ion method