Question

Why is physical adsorption multilayered, whereas chemical adsorption monolayered?

Answer 1

Physical adsorption is multilayered because it involves weak van der Waals forces, which are non-specific; these forces allow multiple layers of adsorbate molecules to accumulate on the adsorbent surface. In contrast, chemical adsorption is monolayered since it requires the formation of strong, specific valence bonds between adsorbate and adsorbent; once a monolayer forms, no further bonding to additional layers can occur. Hence, multilayer adsorption occurs only in physical adsorption, while chemical adsorption is strictly limited to a monolayer.