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SURFACE CHEMISTRY, , , , Terms Related to Adsorption and Absorption, , « Adsorption : The accumulation of molecular species at the surface rather than bulk of solid, or liquid is known as adsorption., , ’, w, , Adsorbate : The molecular species or substance which accumulates at the surface is known, as adsorbate., , io., *, , Adsorbent : The surface at which accumulation of adsorbate takes place is known as, adsorbent., , Ex : Water vapours (adsorbate) adsorb at the surface of silica gel (adsorbent)., , + Desorption : The process of removing an adsorbed substance from adsorbent is known as, desorption. When equilibrium is established then rate of adsorption and rate of desorption, are equal., , Absorption : When atoms, molecules or ions enter in bulk phase of solid or liquid is known, as absorption., , Ex. Water vapours absorbed by anhydrous CaCl., , + Sorption : When adsorption and absorption takes place simultaneously then phenomena is, known as sorption., , eo, ”, , Ex. Dyeing of fabric, , Characteristics of Adsorption, + Adsorption is surface phenomena., + In adsorption enthalpy decreases., + In adsorption entropy decreases., « When decrease in free energy takes place then adsorption takes place.