Question
Is adsorption exothermic or endothermic?
Solution
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 ΔSis negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.
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 ΔSis negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.
