Why is adsorption always exothermic? | Class 12 Chemistry Chapter Surface Chemistry, Surface Chemistry NCERT Solutions

Question:

Why is adsorption always exothermic?

Answer:

Adsorption is always exothermic. This statement can be explained in two ways.

(i) Adsorption leads to a decrease in the residual forces on the surface of the adsorbent. This causes a decrease in the surface energy of the adsorbent. Therefore, adsorption is always exothermic.

(ii) ΔH of adsorption is always negative. When a gas is adsorbed on a solid surface, its movement is restricted leading to a decrease in the entropy of the gas i.e., ΔS is negative. Now for a process to be spontaneous, ΔG should be negative.

ΔG = ΔH - TΔS

Since ΔS is negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.


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Comments

  • Riya
  • 2021-04-15 00:49:00

It helped a great..A Big Thanks to Saral Study!!


  • sufiyan
  • 2019-07-09 09:06:00

Thank you,nice answer


  • Ijay
  • 2019-07-02 07:38:06

Very helpful to me. Thanks a lot


Comment(s) on this Question

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 8: Why is adsorption always exothermic?....