Question

In the reaction:
$Mn{O_2} + 4HCl \to MnC{l_2} + 2{H_2}O + C{l_2}$
(a) Name the compound (i) oxidized, (ii) reduced.
(b) Define oxidation and reduction on its basis.

Answer 1

The given reaction is an example of a redox reaction. In these types of chemical reactions, the oxidation state of atoms or molecules gets changed. Oxidation state can be defined as the total number of electrons gained or lost by an atom while forming a bond with another atom.

Complete step by step answer:
A redox reaction is given as a chemical reaction which is governed via transfer of electrons between two atoms or molecules participating in the reaction. This transfer of electrons is observed by calculating the changes that occur in the oxidation states of the reacting species.
In Redox reactions both oxidation and reduction take place in the same reaction. In this type of chemical reaction, one species is oxidised and the other is reduced.
The molecule in which addition of electrons takes place gets reduced, and the other from which the removal of electrons takes place gets oxidized.
Now, let’s analyse the given reaction:
$Mn{O_2} + 4HCl \to MnC{l_2} + 2{H_2}O + C{l_2}$
(a) (i) $Mn{O_2} + 4{H^ + } + 2e \to M{n^{2 + }} + 2{H_2}O$
As you can see in this reaction, $Mn{O_2}$ is converted to $M{n^{2 + }}$ because addition of electrons takes place in this reaction, hence we can say that $Mn{O_2}$ is the compound which is reduced.
(a) (ii) Now,$2C{l^ - } \to C{l_2} + 2e$
In this reaction, $C{l^ - }$ is oxidized to $C{l_2}$ because removal of electrons takes place. Hence, we can say that the compound which is oxidized is $HCl$.
Now, we will define the Oxidation and Reduction.
(b) OXIDATION: It is defined as loss of electrons or addition of oxygen or it can also be defined as removal of hydrogen. If this phenomenon occurs in any reaction then that reaction is called an oxidation reaction.
REDUCTION: It is defined as gain of electrons or removal of oxygen or it can also be defined as addition of hydrogen. If these phenomena occur in any reaction then that reaction is called a reduction reaction.

Note: Oxidation numbers represent the potential charge present on an atom in its ionic form. If the atom's oxidation is decreased in a reaction, then it is said to get reduced. If it increases, then the atom is said to get oxidized.