The correct statement (S) pertaining to the adsorption of a gas on a solid surface is (are)A. Adsorption is always exothermicB. Physisorption may transform into chemisorption at high temperatureC. Physisorption icnreases with inincreasing temperature but chemisorption decreases with increasing temperatue.D. chemisorption is more exothermic than py sisorption, however it is very slow due to higher energy of aactivation.

The correct statement (S) pertaining to the adsorption of a gas on a s

1.	The correct statement (S) pertaining to the adsorption of a gas on a solid surface is (are)A. Adsorption is always exothermicB. Physisorption may transform into chemisorption at high temperatureC. Physisorption icnreases with inincreasing temperature but chemisorption decreases with increasing temperatue.D. chemisorption is more exothermic than py sisorption, however it is very slow due to higher energy of aactivation.
Answer» Correct Answer - A::C In phtsisorption, with the increase in temperature extent of adsorption decreases (I). Chemisorption first increases with increase in temperature upto a certain extent and then decreases regularly thus (II) is chemisorption. Therefore, (a) is correct option. In chemisorption, attractive forces between adsorbent and adsorbate molecules are strong chemical bonds. As a result, enthalpy of adsorption is high and of the order 80-240 Kj/mol. as in IV `DeltaH_("adsorption")=150KJ//mol`l , thus it also represents chemical adsorption. Therefore (C) is also a correct option.