Question

At which temperature chemical adsorption occurs?
A. Very low temperature
B. High temperature
C. Low temperature
D. Temperature does not affect

Answer 1

To answer the question, first we have to understand adsorption. Adsorption is the phenomenon of accumulation of molecular species at the surface rather than bulk of a liquid or solid.

Complete step by step answer:
Let’s discuss the type of adsorption. There are two types of adsorption, physical adsorption and chemical adsorption. If gaseous molecule accumulates on the surface of solid because of van der Waals' force (weak force), the adsorption is termed as physical adsorption and if the gas molecule is accumulated on the surface of solid by chemical bonds, the adsorption is chemical adsorption.
The chemical bonds formed in chemisorption are of ionic or covalent in nature. They involve a high activation energy so known as activated adsorption. As the formation of chemical bonds occurs in chemical adsorption, high temperature is favorable.

Hence, option B is correct.

Additional Information:
The comparison between physisorption and chemisorption are,

Physisorption	Chemisorption
1)This type of adsorption results due to van der Waal’s force	1)This type of adsorption results due to formation of chemical bond
2)Lacks specificity	2)Specific in nature
3)Enthalpy of adsorption is low	3)Enthalpy of adsorption is high
4)Increases with increase of surface area	4)It too increases with increase of surface are
5)Low temperature is needed for adsorption	5)Higher temperature is needed for adsorption

Note:
Some characteristics of chemical adsorption are, it is very specific in nature and it occurs only when there is possibility of formation of chemical bond between adsorbate and adsorbent. This type of adsorption is usually irreversible in nature.