The reactions in which oxidation and reduction take place simultaneously are known as redox reactions. The oxidation involves the loss of electrons. Whereas the reduction involves the gain of electrons. Redox reactions are classified as; combination, decomposition, disproportionation, and displacement reactions.

What are redox reactions?

“The reactions involved in transferring electrons between two reactants are known as redox reactions.”

The redox reactions consist of two processes oxidation and reduction. These two processes take place at the same time.


“The increase in the number of bonds between carbon and oxygen is known as oxidation ”

During oxidation the oxidation number of atoms increases.

A0→ A+ + e


“The increase in the number of bonds between carbon and hydrogen is known as the reduction.”

During reduction, the oxidation number of atoms decreases.

B0 + e → B-1

Types of redox reactions

The different types of redox reactions are as follow:

  • Decomposition reactions
  • Combination reactions
  • Displacement reactions
  • Disproportionation reactions

Combination redox reaction

“The type of redox reaction in which two atoms or molecules are combined to form a single compound is known as a combination reaction.”


 3Mg + N2 → Mg3N2

 H2 + Cl2 → 2HCl

Decomposition redox reaction

“The reaction in which one molecule breaks into two or more components is known as a decomposition reaction.”

Decomposition reactions are endothermic reactions. This is because they require heat for the reaction. One of the reactants should be in the elemental form.


 Ag2O→ 2Ag + ½ O2

ZnCO3 → ZnO + CO2

2Al2O3 → 4Al + 3O2

All decomposition reactions are not redox reactions. For example,

CaCO3 → CaO + CO2

Displacement redox reactions

“The type of redox reaction in which one atom or ion displaces another atom or ion in a compound is known as displacement reaction.”

Types of displacement reactions

There are two types of displacement reactions.

Metal displacement reaction

“The type of displacement reaction in which one metal present in the compound is displaced by another metal is known as metal displacement reaction.”


CuSO4 + Zn → Cu + ZnSO4

Cu + 2AgNO3 → 2Ag + Cu(NO3)2

Non-metal displacement reactions

“The reaction that mainly involves the hydrogen displacement from the water and acid is known non-metal displacement reaction.”


 Zn + 2HCl → ZnCl2 + H2

2Na + 2H2O → 2NaOH + H2

Disproportionation redox reaction

 “In this type of redox reaction, one element is simultaneously oxidized or reduced.”

This is a special type of redox reaction.


Examples of redox reaction

The examples of redox reaction are the following:

Formation of sodium chloride

In the formation of NaCl, sodium is oxidized whereas chlorine is reduced. The reaction between sodium and chlorine is given below:

  • The oxidation half-reaction is Na → Na+ + e
  • The reduction half-reaction is Cl + e → Cl

The sodium or chloride ion are combined to form sodium chloride.

Combustion of methane

In the combustion reaction, methane is oxidized whereas oxygen is reduced.

  • The oxidation half-reaction is C-4→ C+4 + 4e
  • The reduction half-reaction is O0 + 2e→ O-2

Formation of ferric oxide

In the formation of ferric oxide, iron is oxidized whereas oxygen is reduced.

Formation of ammonia

Nitrogen and hydrogen combine to form ammonia.

N2(g) + 3H2(g) ⇌ 2NH3(g)

  • The oxidation half reaction is H0 → H+ + 1e
  • The reduction half reaction is N0 + 3e → N-3

Examples of redox reactions in daily life

There are many examples of redox reactions in our daily life. Such as:

Cellular Respiration

Cellular respiration involves a series of redox reactions. During this process, glucose is oxidized whereas oxygen is reduced.


“Photosynthesis is a process in which plants use water, carbon dioxide, and sunlight to produce oxygen and energy in the form of sugar. “

In this process, water is oxidized while carbon dioxide is reduced.


“Corrosion is a natural process in which a refined metal is converted into the oxides.”

It is an example of a redox reaction. For example, when the iron is in contact with water, the oxygen atom oxidizes the iron which causes corrosion of it.


Bleaching is another example of redox reactions in our daily life.

“A bleaching agent is a substance which can decolorize the other subtances.”

Concepts Berg

What is an oxidation reaction?

The removal of hydrogen or the addition of oxygen is known as an oxidation reaction.

What is reduction reaction?

The addition of hydrogen or removal of oxygen is known as a reduction reaction.

What are oxidizing agents?

An oxidizing agent is a substance that oxidizes another substance by gaining electrons. For example, halogens, hydrogen peroxide, etc.

What are reducing agents?

In a redox reaction, the reducing agent is a substance that loses electrons to reduce other specie. For example, earth metals, formic acid, etc.

How do determine if a redox reaction has occurred?

When any change occurs in the oxidation number of atoms, whether it increases or decreases then the reaction is redox.

What are the four types of redox reactions?

The four types of redox reaction are as follows:

  • Decomposition reactions
  • Combination reactions
  • Displacement reactions
  • Disproportionation reactions

What is an example of a redox reaction in daily life?

There are some examples of redox reactions in our daily life. Some of them are given below:

  • Photosynthesis
  • Respiration
  • Photography
  • Corrosion
  • Combustion

What is the role of redox reaction in human lives?

Redox reactions have a great influence on human lives. For example, the food we consume to get energy is a redox reaction.

Reference Books

  • Organic Chemistry tenth edition by Francis A. Carey (University of Virginia) and Robert M.Giuliano (Villanova University)

Reference links