Question

Distinguish between chemical and physical adsorption.

Answer 1

The chemical adsorption and physical adsorption are the two main forms by which adsorption takes place. The chemical adsorption is known as chemisorption and physical adsorption is known as physisorption.

Complete step by step answer:
Adsorption is a surface phenomenon where the substance is adsorbed on the surface of another substance. In adsorption mainly two components are required.
(1) Adsorbate: Adsorbate is defined as the substance which is deposited on the surface of the substance.
(2) Adsorbent: Adsorbent is defined as the substance in which the adsorbate is deposited.
The examples of good adsorbent are silica, alumina, charcoal.
The adsorption is characterized into chemical adsorption and physical adsorption.
Chemical adsorption is known as chemisorption and physical adsorption is known as physisorption.
Difference between chemical adsorption and physical adsorption is shown below.
Chemical adsorption:
(1) The chemical adsorption is caused by chemical forces
(2) Chemical adsorption is a strong process.
(3) It is a single layered phenomenon.
(4) The factors affecting chemisorption are surface area, temperature, nature of adsorbate.
(5) Chemical adsorption is highly specific in nature and takes place at the center of the adsorbent.
Physical adsorption:
(1) The physical adsorption is caused by physical forces.
(2) The physical adsorption is a weak process.
(3) In physical adsorption multi layers are formed.
(4) The factors affecting physical adsorption are pressure, surface area, temperature.
(5) Physical adsorption is not specific in nature and can take place all over the adsorbent.

Note:
As temperature is the most important factor which affects the adsorption process, the adsorption is described by isotherms. Freundlich adsorption isotherm and Langmuir adsorption isotherm is used to describe the adsorption process.