Question

Chemisorption is ............ while physical adsorption is ........... in nature.

• A. reversible, reversible
• B. irreversible, reversible
• C. reversible, irreversible
• D. irreversible, irreversible

Answer 1

Answer: (B)

irreversible, reversible

Chemisorption is irreversible process while physical adsorption is reversible in nature.
Chemisorption is an adsorption where the forces involved are valence forces of the same kind as those operating in the formation of chemical compounds. Thus, chemisorption leads to formation of the so called a "surface compound". The process is irreversible. Efforts to free the adsorbed gas give some definite compound.
Physisorption is adsorption in which the forces involved are intermolecular forces (van der Waals forces) of the same kind as those responsible for the imperfection of real gases and the condensation of vapours. The process is reversible, i.e., desorption of the gas occurs by increasing the temperature or decreasing the pressure.