Question

How does adsorption reduce the net enthalpy of the system?

Answer 1

Absorption is a exothermic reaction and it has negative sign so it will reduce the net enthalpy of the system

Detail explanation

Net enthalpy of the system = Initial enthalpy + absorbtion enthalpy. Since absorption is a exothermic process and has negative sign so net enthalpy of the system will decrease.


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.