Question

What is chemisorption?

Answer 1

Hint: The phenomenon of attracting and retaining the molecules of a substance at the surface of a solid or liquid, resulting in a higher concentration of molecules on the surface than in bulk. It occurs due to the residual unbalanced forces existing on the surface of a solid or liquid. The more the surface area the greater is the adsorption. The gas or vapour or the solute that accumulates at the surface of an adsorbent is called an adsorbate. The solid material on whose surface the gas or vapour or solute gets adsorbed is called an adsorbent. Adsorption is of 2 types: physisorption and chemisorption.

Complete step by step solution:
Chemisorption can occur at all temperatures. This process increases with an increase in temperature. It is irreversible in nature, that is, adsorbate cannot be recovered from the adsorbent easily. The chemisorptions can operate over short distances. It does not extend beyond a monolayer of gas molecules or atoms on the surface of a solid.

The adsorbate molecules are held strongly by strong chemical forces. Hence, the activation energy of desorption is very high. Desorption means the process of removing an adsorbed substance from a surface on which it is adsorbed.

Note: The rate of adsorption is initially very high due to the large availability of surface area, but afterwards it decreases. Adsorption is an exothermic process, meaning energy is released during the process. Chemisorptions produce a large amount of energy, ranging from 40 to 400 KJ/mol.