The correct statement(s) pertaining to the adsorption of a gas on a solid surface is(are)
(i) adsorption is always exothermic
(ii) physisorption may transform into chemsisorption transform into chemisorption at high temperature
(iii) physisorption increases with increasing temperature but chemisorption decreases with increasing temperature .
(iv) chemisorption is more exothermic than physisorption , however it is very slow due to higher energy of activation.

Options

A. Adsorption is always exothermic.
B. Physisorption may transform 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

A, B, D

Explanation

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

d. It is a factual statement.