Redox Reactions

Classical Idea of Redox Reactions

What is oxidation? Have you seen the rusting of iron articles? Yes, all of us at some point or the other have seen rusting of an iron object. It is nothing but an example of a redox reaction, oxidation and reduction reaction. Redox reactions form the basis of many biological and physical phenomena.

Fading of colours from your clothes, burning of different kind of fuels or combustible substances such as wood, coal, to obtain energy for commercial, domestic and transport purposes. These are the examples of oxidation and reduction, redox, reactions.

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Classical Idea of Redox Reactions

Additionally, many sectors including biological, industrial, pharmaceutical, metallurgical and agricultural employes redox reaction in different processes. Some very common industrial process examples for redox reactions are electroplating, extraction of metals such as aluminium, manufacture of chemical compounds such as caustic soda, bleaching of wood pulp, corrosion of metals, the operation of batteries and many more.

Even many environmental issues concerning Ozone hole is being linked redox reaction phenomenon. So let’s study the classical idea of redox reactions. Redox reactions consist of two reactions- oxidation and reduction taking place hand in hand. that is, simultaneously. Let’s study each of these reactions individually and in detail.

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What is Oxidation?

Initially, oxidation meant the addition of oxygen to a compound or an element. The reason for the prevalence of such a term was the presence of dioxygen in the atmosphere and its reaction that commonly occur in the earth. We know the percentage of oxygen in the atmosphere is nearly 20 percent.

Soon chemists started realizing that this was to be the key reason why many elements occur in the atmosphere in their oxide form. There were several limitations in the definition. However, with the limited information available at that time, the reactions are

what is oxidation

In the above two reactions, magnesium and sulphur oxidize due to the addition of oxygen to them. Another such example is oxidation of methane by addition of oxygen.

oxidation and reduction

However, in the above reaction exchange of hydrogen by oxygen led scientists to broaden the definition and reinterpret it. Therefore, “removal of hydrogen from a substance” was included in the original definition. Another example that proves “removal of hydrogen as an example of oxidation.”


Gradually, the knowledge of chemists grew and the understood oxidation involves other electronegative elements as well. Thus, the reaction is possible for magnesium, chlorine, sulphur, and fluorine.

Examples of Oxidation


The above reactions helped chemists to understand that not only removal of hydrogen but the removal of the electropositive element also is part of the oxidation process. Therefore in the reaction mentioned below depicts an oxidation reaction where removal of the electropositive element takes place.


Initially, there was a limitation in the definition of reduction.  The reduction process refers to the removal of oxygen from an element or a compound. Reinterpretation of the term led to a new definition. Now, reduction refers to the removal of oxygen or electronegative element from a compound/substance or it also refers to the addition of hydrogen or electropositive element to a substance. Refer to examples below to understand reduction process.

Examples of Reduction


In the third reaction of the above example, oxidation and reduction occur simultaneously. In the reaction conversion of stannous chloride to stannic chloride is an example of addition of electronegative element chlorine. Therefore, it is an example of oxidation. Therefore, soon chemists realized that oxidation and reduction can occur simultaneously. Reevaluation of all the points led to coining the term “redox” to the complete oxidation and reduction process.

Learn Redox Reactions as the basis of Titration here. 

Solved Question for You

Q: Determine the species undergoing the oxidation and reduction

Solution: In the above reaction, H2S is oxidized because of the presence of the more electronegative element in the reaction. Therefore, the addition of chlorine to hydrogen occurs and a more electropositive element “hydrogen” removal occurs from sulphur. Therefore, chlorine is reduced as a result of the addition of hydrogen.

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