Question

What is the difference between physisorption and chemisorption?

Answer 1

Hint: Physisorption and chemisorption are the types of adsorption. Adsorption can be referred to as the accumulation of the molecular species at the surface instead of the solid and liquid bulks.

Complete step by step answer:
Adsorption is usually a surface phenomenon. During this the molecules of the solvent get adsorbed at the surface of the solute. Adsorption is of two types: physisorption and chemisorption. The difference between these two is given below.

Physisorption	Chemisorption
1. It is also known as physical adsorption.	1. It is also known as chemical adsorption.
2. The reason behind physisorption is Van der Waals forces.	2. Chemical bonds lead to chemisorption.
3. Physical adsorption is reversible in nature.	3. Chemical adsorption is irreversible in nature.
4. It is not at all specific in nature.	4. It is very specific in nature.
5. Physisorption has a very low adsorption enthalpy of nearly about 20 to 40 kJ/mol.	5. Chemisorption has higher adsorption enthalpy, nearly about 80 to 240 kJ/mol, than that of physisorption.
6. It takes place favourly in low temperatures.	6. It takes place favourly in high temperatures.
7. As the temperature increases the amount of physisorption taking place decreases.	7. As the temperature increases the amount of chemisorption taking place increases.
8. Since physisorption has weak Van Der Waal forces, it results in a multimolecular layer.	8. Since chemisorption is formed through covalent bonds which are very strong bonds, therefore, it results in a unimolecular layer.
9. Physical adsorption has less activation energy.	9. Chemical adsorption has high activation energy.

Note: Both physisorption and chemisorption are surface phenomena. They both are exothermic in nature. They both increase with the increase in the surface area. And both are associated with the decrease in entropy.