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Question:

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

Adsorption is always exothermic.

Physisorption may transform into chemisorption at high temperature.

Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.

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

Solution:

ΔH = −ve for adsorption and hence, adsorption is always exothermic. Besides, physisorption may transform into chemisorption at higher temperatures since it will provide sufficient energy for chemical reaction to take place.