Question

Adsorption of gas on a solid is always exothermic explain?;;

Answer 1

Answer:

Explanation:

Adsorption of gas on a solid is a spontaneous process. When a gas adsorbs on the solid, due to molecular interaction process, the entropy of gas molecules decreases. To make the process spontaneous, adsorption must be exothermic.

Answer 2

Adsorption of gases on the solid surface is generally exothermic. 

According to this statement, H=−ve and  condition for spontaneous process is G=−ve. 

During adsorption, S=−ve, then −TS must be positive according to the above equation. 

Now, reaction can only be spontaneous or G=−ve only if H=−ve. 

Hence, adsorption of gases on a solid surface is generally exothermic because of a decrease in entropy.