• Adsorption is a surface phenomenon by which ions or molecules of gas, liquid or solid gets adhered to any surface.
• It is an exothermic process and heat of the adsorption is processed up in enhancing the rate of the reaction.
• Due to this, the randomly oriented molecules of the gas or the liquid are organised on the surface of the solid.
• This organisation decreases the entropy. Thus change in entropy is negative.
• So, ΔS is negative.
According to the Gibbs free energy equation,
• for a spontaneous process, ΔG is negative.
• Now, ΔG can only be negative if and only if ΔH is negative, which means evolution of heat or the process is exothermic.
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