What is oxidation or reduction?

Oxidation and reduction are most common words when you study chemical reactions. What happens in a chemical reaction? Two reactants react together and form the product and by-products. When you view it closely you will find that a chemical reaction is nothing but a kind of business where they exchange electrons instead of money. In any reaction the total number of electrons remains constant, they only move from one species to other so that one species gets profited by gaining electrons and the other suffers a loss by losing electrons. Oxidation and reduction refer to the state of loser and gainer.

Let’s take an example to understand it:

Sn⁴⁺ + Fe ⟶ Fe²⁺  + Sn²⁺

Notice the oxidation number of tin and iron on both sides of the arrow. Oxidation number gives us an idea about an element's willingness to give its electron. Either it likes to donate or accept electrons. In the above reaction:

Sn(IV) ⟶ Sn(II)

Fe(0) ⟶ Fe(II)

Oxidation number of tin was +4 and it becomes +2. It gains 2 electrons. And its oxidation state reduces from 4 to 2. We can say that Sn(IV) is reduced to Sn(II). Now we can define reduction as a process in which element gains electrons and it oxidation number reduces.  

In the case of iron, its oxidation number was (0) and after the reaction it becomes (+2). It loses 2 electrons and its oxidation state increases from 0 to 2. This process is called oxidation. Here iron Fe(0) gets oxidised to Fe(II).

In the above reaction iron Fe(0) gets oxidised by tin Sn(IV), so tin Sn(IV) acts as an oxidising agent. And tin Sn(IV) get reduced by iron Fe(0) so iron Fe(0) acts as a reducing agent.

In the above reaction Sn(IV) gives 2e^- to Fe(0) to get it oxidised to Fe(II) state or you can say Fe(0) gets oxidised by Sn(IV). Here Sn(IV) acts as an oxidising agent. After giving 2e^- to iron tin itself gets reduced to Sn(II) state.

If you see above reaction in a different prospect, Fe(0) accepts electrons from Sn(IV) so that it can get reduced to Sn(II) state, in this way Sn(IV) gets reduced by Fe(0). Now Fe(0) acts as reducing agent which itself gets oxidised to Fe(II) state.

Such reactions are called redox reactions, where oxidation and reduction takes place simultaneously, as happened in the above reaction where Sn(IV) gets reduced and Fe(0) gets oxidised simultaneously. Redox reactions are very useful and important reactions; we will study them in coming posts.

This work is licensed under the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.