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 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 but it is very slow due to higher energy of activation

Answer 1

Adsorption is a surface phenomenon, a physical property in which the reaction takes place on the surface of the adsorbent. It depends on multiple factors.

Complete step by step solution:
With increase in temperature, the reversal of adsorption i.e. desorption favors that means with decrease in temperature adsorption increases or favors. Decrease in temperature is condensation which is exothermic, so adsorption is exothermic. Physisorption or physical adsorption increases with decrease in temperature but chemical adsorption or chemisorption increases with increase in temperature. Chemisorption is not exothermic, it is endothermic involving the intake of energy and it also favors high activation of energy. When temperature increases Physisorption transforms to chemisorption the rate of the reaction increases with increase in temperature.

So the solution of the above question is multi correct type. The answers for the given question lie in option (A) adsorption is always exothermic, option (B) Physisorption may transform to chemisorption at high temperature.

Note: The adsorption of gas on the solid surface depends on factors such as the nature of gas. The extent of adsorption of every gas is different and it is affected by critical temperature.