Thermodynamics of Gas Adsorption on Solid Surface

From physicochemical principles, it is known that any pure surface, especially solid, means that it is surrounded by no other foreign molecule (which means it is under vacuum). However, as soon as there is a foreign molecule in the gas phase, the latter will adsorb to some extent depending on the physical conditions (temperature and pressure). On any solid surface, gas will adsorb or desorb under specific conditions (e.g., in gas recovery from shale deposits). Gas molecules will adsorb and desorb at the solid surface as determined by different parameters. At equilibrium, the rates of adsorption (R ) and desorption (R j) will be equal. The surface can be described as consisting of different kinds of surfaces  

Area of clean surface = Aq Area covered with gas = A  

Enthalpy of adsorption = (energy required to adsorb a molecule from gas phase to the solid surface) 

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