Oxidation and reduction reactions

In chemistry, the reactions which involve the transfer of electrons from one chemical substance to another are the ones that are known as oxidation-reduction reactions or redox reactions. These electron transfer reactions or oxidation-reduction reactions are accompanied by energy changes in light, heat, and electricity. Usually, reactions also involve the addition of hydrogen and oxygen in their respective equations. 

Students might have heard a lot of words like redox, oxidation-reduction reactions, transfer-charge reactions, etc. Now, let us discuss from where do these terms in chemistry originate from? 

What is oxidation in chemistry? How is reduction different from oxidation? And if they are different, how do oxidation and reduction go together in a reaction? Let us answer all your questions here. 

What is Oxidation?

Ironically, oxidation reactions have nothing to do with oxygen; the definition of oxidation reaction states that when an ion, an atom, or a molecule loses electrons as a part of their reactions, such a process is called oxidation.

Oxidation occurs when, in any reaction, the oxidation state of a molecule, atom, or ion increases.

What is an Oxidation State? 

Oxidation state is termed as the degree of oxidation of an atom in a molecule. In simpler words, the oxidation state is the charge of an atom if all bonds it formed were ionic bonds.

For example:- A classic example of an oxidation reaction at work is rusting of iron. The chemical reaction involved in the rusting process of iron or any other metal is termed an oxidation reaction as the oxidation state of the metal on which the layer of rust forms increases. Here oxygen gets added to Iron to make Iron Oxide. You can look at it from the perspective of oxygen gaining electrons from a stable state. This reaction is written as:

2 Fe + O2 → Fe2O3

Another very popular example of the oxidation reaction is where an element combines with oxygen in the reaction between magnesium metal and oxygen to form magnesium oxide. In this case, we experience the same nature as the oxidation state of the final product increases.
This reaction can be written as: 

2 Mg (s) + O2 (g) → 2 MgO (s)

Reduction Reactions

As their name suggests, a reduction reaction is when hydrogen or any other electropositive charge is added to an element. Oxygen is removed from the reaction. 

Reduction reactions can be termed as the opposite of oxidation reactions as well. A reduction reaction involves a half-reaction in which chemical species decrease their oxidation number by gaining electrons. 

Examples of reduction reactions 

1. This equation can be termed as the most popular when it comes to reduction reactions. According to this equation, the H+ ions, with oxidation number of +1, are reduced to H2, with the oxidation number 0. This chemical reaction is thus written as:

Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)

2. Another example is the reaction between copper oxide and magnesium to yield copper and magnesium oxide. The reaction is chemically written as:

CuO + Mg → Cu + MgO

There is another type of reaction that combines oxidation and reduction simultaneously. These reactions are also known as redox reactions. The term ‘redox’ is derived from reduction-oxidation by taking the initial letters of both processes. All the redox reactions consist of two consecutive processes, i.e. a reduction process and an oxidation process. 

What are Redox Reactions? 

A reaction in which the electrons are transferred between the two reactants participating in the reaction is called a Redox Reaction. This transfer of electrons plays its role by changing the oxidation states of the reacting species and the reduction in the oxygen particles. During a redox reaction, oxidation and reduction coincide. The total transfer of electrons forms the base of the redox reactions.

There are four different redox reactions. All of them are mentioned below: 

 Decomposition Reaction

As the name of the reaction says, these kinds of reactions involve decomposition of a compound into different compounds. Some examples of these types of reactions are:

• 2NaH → 2Na + H2

• 2H2O → 2H2 + O2

Combination Reaction 

Unlike decomposition reactions, combination reactions are the reactions which involve the combination of two compounds to form a single compound in the form of A + B → AB. Some examples of combination reactions are given below:

• H2 + Cl2 → 2HCl

• C+O2→CO2

• 4 Fe+ 3O2→2Fe2O3

Displacement Reaction

When an atom or an ion of some element is replaced by another atom or an ion of some other element, such types of reactions are known as Displacement Reactions. It can be represented in the form of X + YZ → XZ + Y. 

Displacement reaction can be briefly divided into the following reactions-

• Metal displacement Reaction

• Non-metal displacement Reaction

Some of the examples of displacement reactions are given below: 

• CuSO4+Zn→Cu+ZnSO4

Disproportionation Reactions

In this type of reaction, a single reactant is oxidised and reduced, which is why these reactions are known as Disproportionation Reactions. Some of the examples of disproportionation reactions are given below: 

P4 + 3NaOH + 3H2O → 3NaH2PO2 + PH3

Conclusion

Now we all know the definition and meaning of some of the most commonly used terms in chemistry. We also learned about the difference between oxidation and reduction and their respective reactions. We hope all your doubts have been cleared after reading this article and you got a piece of deep knowledge about the topic as well.