Monday, September 22, 2014

Free Energy Change of Adsorption

Since adsorption is Exothermic Reaction. Therefore for adsorption ΔH is always negative and favours the process. Also adsorption leads to decrease in entropy i.e. ΔS is negative because the adsorbate molecules gets lesser opportunity to move about on the surface of adsorbent. According to Gibbs - Helmholtz Equation.
ΔG = ΔH – TΔS
Since adsorption is Spontaneous Process, hence ΔG is negative or ΔH > TΔS. As adsorption continues, the difference between two opposing factors becomes lesser and lesser till they becomes equal i.e ΔH = TΔS or ΔG = 0. At this stage, Equilibrium called Adsorption Equilibrium is established and hence no adsorption takes place at this stage.