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NCERT Class 11 Chemistry Chapter 8 Notes Redox Reaction - Download PDF

NCERT Class 11 Chemistry Chapter 8 Notes Redox Reaction - Download PDF

Edited By Sumit Saini | Updated on Apr 09, 2024 02:57 PM IST

The NCERT Class 11 Chemistry chapter 8 Notes covers a brief outline of the chapter redox reactions. The main topics covered in redox reaction Class 11 notes are Electrochemical cells, Salt bridge, Standard hydrogen electrode, Oxidation, and redox reactions. Class 11 Chemistry chapter 8 notes are helpful in covering the major and minor topics such as Redox reactions in terms of electron transfer reactions, Oxidation number-types of redox reaction. With the aid of redox reaction class 11 notes, students can enhance their knowledge and proficiency in this fundamental area of chemistry.

The Class 11 Chemistry chapter 8 notes are the best way to individually conceptualize the balancing of a redox reaction, redox reactions as the basis for titrations, limitations. Class 11 Chemistry chapter 8 notes include different types of reaction mechanisms which are as important for the examination point of view and by this students are able to score well in CBSE Class 11 Chemistry examinations. Additionally, ch 8 chemistry class 11 notes offer detailed explanations and examples to help students grasp the concepts effectively.

Also, students can refer,

NCERT Class 11 Chemistry Chapter 8 Notes

Topic-1 Electrochemical Cell:

It is a device in which the redox reaction is carried out indirectly and decreases in free energy appeals as electrical energy.


Salt Bridge:

It is a U-shaped tube filled with agar-agar containing inert electrolytes like potassium chloride or potassium nitrate which does not react with solutions.

Standard hydrogen electrode:

It is also referred to as a reference electrode. The electrode potential of the standard hydrogen electrode is 0.000 volt.

Oxidation and Reduction reactions:

Oxidation is an increase in oxidation number, Whereas Reduction is a decrease in oxidation number in Redox reactions.

Topic-2 Redox Reactions in Terms of Electron Transfer Reactions,

Splitting the reaction into two half-reactions clearly suggests the oxidation of Sodium and reduction of Hydrogen. Loss of electrons in any substance means oxidation of that substance occurs whereas gain in any substance signifies the reduction process. Therefore, we can say that the complete reaction itself is a Redox reaction.

2Na(s)+H2(g)→2NaH(s) is an example of redox change.

The half reaction is:


The other half-reaction is:


Topic-3 Oxidation Number:

Oxidation number can be defined as the bond formation of ionic bonds with other heteroatoms and at the same time attaining the charge on that atom.

For example:

The oxidation number for different metal ions:

All alkali metal ions are always having a +1 oxidation state

All alkaline earth metal ions are always having a +2 oxidation state.

Types of Redox reaction:

A redox reaction can be defined as a chemical reaction in which we can see the transfer of electrons occur in between two reactants i.e. one is going to be reduced and the other is going to gain that electron.

Decomposition reaction:

This type of reaction involves breaking a compound into other different compounds.


  • 2NaH → 2Na + H2

Combination reaction:

These types of reactions are opposite to decomposition reactions. So the combination of two compounds produces a single product.


4Fe+ 3O2→2Fe2O3

Displacement reaction:

This is a type of reaction where an atom or ion is replaced by another atom or ion according to its reactivity level. It can be categorized into:

  • Metal displacement Reaction

  • Non-metal displacement Reaction

Metal Displacement reaction:

This type of reaction involves when a metal present in a particular compound is displaced by another metal. This type of reaction can be seen in the metallurgical process where extraction of ores can be done from their respective metals.

For example CuSO4+Zn→Cu+ZnSO4

Non-Metal Displacement reaction:

This type of reaction involves the displacement of hydrogen and in rare oxygen, displacement can be observed.

Disproportionation reaction:

This is the type of reaction in which reduction and oxidation occur on the same compound or element.

For example:

3Cl2 + 6NaOH→ 5NaCl+NaClO3 +3H2O

Balancing of redox reaction:

The two ways through which we can balance the redox reaction;

First method: In this method by a change in the oxidation number of oxidizing agent and the reducing agent.

Second method: In this method dividing the redox reaction into two half-reactions in which one is being oxidized and the other is getting reduced.

Redox Titrations on basis of titrations:

In the process of titration, oxidation-reduction reactions occur and are known as redox titration. During the chemical reaction in such a technique transfer of electrons can be seen in the aqueous solution.

The Redox titration can further be classified on the basis of the reagent used in the redox titration.

Sub-Divisions of Redox Titrations

  • Permanganate Titrations

  • Dichromate Titrations

  • Iodometric and Iodometric Titrations

Topic-4: Limitation of The Concept of Oxidation Number:

It is not practically possible to apply the classical approach where the oxidation number concept is verified; the reaction is the so-called Redox reaction.

Redox reactions and electrode processes:

A redox couple is defined as when a substance is taking part in the oxidation and reduction process- half-reaction the combination of both oxidized and reduced parts of the substance is present in that reaction.

The electrode potential of a Galvanic cell can be defined as the tendency of losing or gaining the electrodes.

Dependency of electrode potential:

The electrode potential can be dependent upon:

  • Nature of the metal,

  • The concentration of the ions and

  • The temperature of an electrolyte

Significance of NCERT Notes for Chemistry Chapter 8 Notes:

The Redox reactions Class 11 notes focus on the important points regarding the oxidation and reduction reactions. The students can strategize their study plan with the help of cbse class 11 chemistry ch 8 notes. The main goal is to achieve good marks with proper guidance and the best methodological approach. The chemistry class 11 chapter 8 notes pdf download can be downloaded with no extra cost and students can access it offline as well. The important Redox reactions and another different reaction mechanism with their example are given so that students didn’t find any difficulty while writing the answers in the CBSE Class 11 Chemistry examinations. In conclusion, cbse class 11 chemistry ch 8 notes
provide a comprehensive framework for understanding redox reactions, empowering students to navigate the complexities of chemistry with clarity and proficiency.

NCERT Class 11 Notes Chapter-Wise

Subject Wise NCERT Exemplar Solutions

Subject Wise NCERT Solutions

Frequently Asked Question (FAQs)

1. 1. What are oxidation-reduction reactions as per notes for Class 11 Chemistry chapter?

Oxidation-reduction reactions are chemical reactions that involve the transfer of electrons between the reacting species. These electron transfers are accompanied by a change in the oxidation state of the reactants. chemistry class 11 chapter 8 notes pdf can be referred for more understanding on the topic. 

2. 2. What are oxidizing agents according to ncert notes for Class 11 Chemistry chapter 8?

An oxidizing agent is an electron-accepting species that is readily reduced in an oxidation-reduction reaction. The oxidation numbers of these species tend to decrease in redox reactions.  Examples are nitric acid and hydrogen peroxide. Students can refer ch 8 chemistry class 11 notes for more understanding of the topic. 

3. 3. What are reducing agents according to Class 11 Redox reaction notes?

Reducing agents are the electron-donating species that readily undergo oxidation in oxidation-reduction reactions. These species tend to lose electrons in redox reactions and their oxidation number increases. Examples: zinc and lithium.

4. 4. What are the significant conditions that must be fulfilled in a redox reaction?

The conservation of electrons should not be conflicted. 

The total number of electrons lost or gained is equal. This can be done using an oxidizing agent.

5. 5. While oxidation of a compound or reaction the effect of oxidation number implies to what?

During oxidation, the oxidation number will increase. 

If in case the oxidation number of an element changes its oxidation state from 0 to +1. Then this change is accompanied by oxidized change.


Get answers from students and experts

A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg


An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)


Option 2)

\; K\;

Option 3)


Option 4)


In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)


Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)


Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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