Understanding Redox Reactions: A Complete Guide

Learn everything you need to know about redox reactions, its types, methods, examples from balancing equations to real-life applications.

Sarah Taylor-

Published on 2023-05-22




A redox reaction is a fundamental concept in chemistry. It involves the transfer of electrons between reactants, leading to a change in oxidation states. Redox or oxidation-reduction reactions are essential in many natural processes and industrial applications.

We will discuss the basics of redox reactions, definitions, examples, and applications. This article will also have redox reaction examples, methods, and real-life applications.

Let's start with the question of what exactly redox reactions are.

What are redox reactions?

Redox reactions, sometimes known as oxidation-reduction reactions, are a type of chemical process in which electrons transfer from one reactant to another. Typically, in these reactions, electrons are transferred from one reagent to another, changing the oxidation state of the reactants.

What is oxidation?

Oxidation is a chemical reaction in which a reactant changes its oxidation state or loses electrons. A reactant is oxidized during an oxidation reaction, shedding electrons and acquiring a more positive charge.

What is reduction?

Reduction is a chemical process that involves the gain of electrons or a decrease in the oxidation state of a reactant. In a reduction reaction, the reactant gains electrons and becomes more negatively charged, indicating it undergoes reduction.

Types of Redox Reaction 

There are several types of redox reactions, including direct and indirect redox reaction, oxidation-reduction, combination, decomposition, and displacement reactions.

Oxidation-reduction reactions involve the transfer of electrons between two species, while combination reactions involve the formation of a single product from two or more reactants. 

Decomposition reactions involve the breakdown of a single reactant into two or more products, and displacement reactions involve the exchange of atoms or ions between two reactants. 

Direct Redox Reaction

A direct redox reaction involves the transfer of electrons directly from the reducing agent to the oxidizing agent. This type of reaction can be seen in simple reactions such as the reaction between copper and silver nitrate:

 Cu + 2AgNO3 → Cu(NO3)2 + 2Ag

In this reaction, the copper metal is oxidized (loses electrons) and the silver ions are reduced (gain electrons) directly.

Indirect Redox Reaction

An indirect redox reaction involves the transfer of electrons through an intermediate species. One common type of indirect redox reaction is the use of a mediator, such as an enzyme, to transfer electrons from the reducing agent to the oxidizing agent. An example of an indirect redox reaction is the reaction between glucose and oxygen in cellular respiration:

 C6H12O6 + 6O2 → 6CO2 + 6H2O

In this reaction, glucose is oxidized to carbon dioxide and oxygen is reduced to water, but the electrons are transferred through a series of intermediate steps involving enzymes and other molecules.

Electron transfer

Electron transfer is a process that occurs during redox reactions. During these reactions, one reactant loses electrons while another gains electrons.It is also the process of Electrochemistry 

Reactions that are enabled by the passage of electrons from one to another result in the cause of new chemical bonds, the release of energy, or the creation of an electric current.

Electron transfer can occur in various forms, from the combustion of fuels to the production of electricity in batteries. 

Oxidation state

The oxidation state, also referred to as the oxidation number, measures how much an atom in a substance has been reduced. It indicates whether an atom has gained or lost electrons compared to its neutral state.

If an atom has gained, lost, or kept its electrons, the oxidation state can be positive, negative, or zero. Electrons are transferred between the reactants and products in a redox reaction, causing a change in their oxidation states.

What is a reducing agent?

A reducing agent is a substance that causes another substance to be reduced, meaning it donates electrons to the substance being reduced. This causes the reducing agent to be oxidized, as it loses electrons.

In a redox reaction, the reducing agent undergoes oxidation as it donates electrons to the oxidizing agent. 

What is an oxidizing agent?

An oxidizing agent is a substance that causes another substance to be oxidized, meaning it accepts electrons from the oxidized substance. It reduces the oxidizing agent as it gains electrons.

In a redox reaction, the oxidizing agent undergoes reduction as it accepts electrons from the reducing agent. As it gains electrons, it reduces the oxidizing agent.

Applications of redox reactions

Redox reactions have a variety of practical applications in many different fields, including industry, medicine, and energy production. Here are a few examples:


Redox reactions are used in the electroplating technique to apply a thin layer of another metal to metal objects. In this method, the metal object that will be coated becomes a cathode, and the metal that will be coated becomes the anode of an electrolytic cell. 

As a current passes through the cell, the metal ions from the anode are reduced and deposited onto the cathode, resulting in a thin layer of metal coating the object.

Corrosion prevention techniques

Redox reactions are also important in preventing corrosion, which is the gradual degradation of materials due to environmental exposure. One method of preventing corrosion involves using redox reactions to create a protective layer on the material's surface.

 For example, An oxidizing agent is applied to a metal surface during the metallization process to create a thin oxide layer that shields the metal from further oxidation.


Batteries also rely on redox reactions to produce an electric current. In a battery, a redox 

reaction occurs between two electrodes, one is the anode, and the other one is the cathode. As the reaction occurs, electrons flow from the anode to the cathode, producing an electric current that can be used to power electronic devices.

Examples of Redox Reactions

Redox reactions are ubiquitous and have a wide range of applications. Here are a few examples of redox reactions:


Combustion is a common redox reaction in which a hydrocarbon is involved with oxygen to produce carbon dioxide and water. In combustion, the fuel is oxidized while oxygen is reduced.


 Photosynthesis is another important redox reaction that occurs in plants and algae. In this procedure, carbon dioxide and water are transferred into glucose and oxygen with the help of sunlight. During photosynthesis, water is oxidized while carbon dioxide is reduced.


 Rusting is a redox reaction that occurs when iron reacts with oxygen in the water to form hydrated iron(III) oxide, also known as rust. In this process, oxygen reduces while iron oxidizes.


Respiration is a redox reaction in living organisms, where glucose is oxidized to produce energy, carbon dioxide, and water. While respiring, the organism oxidizes glucose and reduces oxygen.

Redox Experiments

Redox experiments are widely used in chemistry to study redox reactions. Some examples of redox experiments are:

Redox Titration

This technique is used to determine a solution's concentration by reacting it with the known amount of another solution of known concentration.

In the iodometric titration of vitamin C, iodine oxidizes vitamin C to dehydroascorbic acid in the presence of an acid. Then a standard sodium thiosulfate solution is used to titrate the excess iodine.


Electrolysis is a non-spontaneous redox reaction produced by an electric current during the process. 

For example, water is reduced at a cathode to form hydrogen gas and is oxidized at an anode to form oxygen gas at water electrolysis.

Cellular Respiration

Cellular respiration is a redox reaction that occurs in all living cells, where glucose is oxidized to produce energy in the form of ATP. The main steps of cellular respiration are:


Glucose is broken down into pyruvate, producing a small amount of ATP and NADH.

Krebs cycle

 The pyruvate is then further oxidized in the mitochondria, producing more ATP and reducing power in NADH and FADH2.

Electron Transport Chain 

The NADH and FADH2 produced in the Krebs cycle are then used to drive the electron transport chain, which generates a large amount of ATP through oxidative phosphorylation.

Balancing Redox Reactions

Calculating the oxidation states of the products and reactants and adjusting the coefficients to make sure that the number of electrons lost by the oxidizing agent is equal to the number of electrons obtained by the reducing agent is balancing redox reactions, which is a useful technique in chemistry. Some important steps in balancing redox reactions are:

Identify the reactants and products and write their oxidation states.

  • Determine which species is oxidized and which species is reducing.
  • Balance the number of atoms of each element on both sides of the equation.
  • Add H+ or OH- ions to balance the charges.
  • Balance the number of electrons by adding or subtracting electrons as needed.
  • Check that the final equation is balanced and that the oxidation states of the reactants and products are consistent with the rules of redox reactions.

Methods of Balancing Redox Reactions

Balancing Redox Reactions involves the transfer of electrons between species. One common method is the half-reaction method, which separates the reaction into an oxidation and reduction half-reaction. 

Another method is the oxidation number change method, which involves assigning oxidation numbers to the species in the reaction and then adjusting coefficients to balance the overall change in oxidation number. Both methods require careful consideration of the reaction conditions and species involved.

Note:You can also use redox reaction calculatorto balance your equation.


Redox reaction is a part of inorganic chemistry.

Yes, redox reactions are a fundamental part of inorganic chemistry, which deals with the study of the chemistry of inorganic compounds and elements.

What causes a redox reaction?

A redox reaction occurs when there is a transfer of electrons between the reactants, leading to a change in the oxidation states of the atoms involved.

What is an exothermic redox reaction?

An exothermic redox reaction is a reaction that releases energy in the form of heat as a result of the transfer of electrons between the reactants.

How to know if a redox reaction is spontaneous?

A redox reaction is spontaneous if the Gibbs free energy change (∆G) is negative, indicating that the reaction will occur spontaneously and release energy.

Why are redox reactions important?

Redox reactions are important because they are involved in many chemical and biological processes, including energy production, metabolism, and oxidation of pollutants in the environment.

In a redox reaction, why does an element's oxidation number increase?

An element's oxidation number increases in a redox reaction when it loses electrons (i.e., undergoes oxidation), as the oxidation number is a measure of the element's electron loss or gain.

What two things must be balanced in a redox reaction?

In a redox reaction, both the number of electrons and the total charge must be balanced to ensure that the reaction follows the principle of conservation of charge.

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