Question

The correct statement(s) pertaining to the adsorption of a gas on a solid surface is (are)

• A. Adsorption is always exothermic.
• B. Physisorption may transformation into chemisorption at high temperature.
• C. Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.
• D. Chemisorption is more exothermic than physisorption; however, it is very slow due to higher energy of activation.

Answer 1

Answer: (A), (B), (D)

Chemisorption is more exothermic than physisorption; however, it is very slow due to higher energy of activation.

a. Adsorption is always exothermic (factual statement).
b. It is also a factual statement.
c. The statement is wrong. Physisorption decreases with increase in temperature. But chemisorption first increases with increase in temperaure and then decreases. The effect is called activated adsorption.

d. It is a factual statement.