Question

physical adsorption is multilayeres whereas chemisorption is monolayered

Answer 1

Physical adsorption involves only weak intermolecular forces between the solid medium and the gaseous phase. When there is complete coverage of the solid surface a second layer can form by interaction of the adsorbed layer with more material in the gaseous phase and multilayers can build up. In chemical adsorption there is a chemical bond between the solid surface and the adsorbed material. This is much stronger than the weak intermolecular forces involved in physical adsorption. Once you have a monolayer molecules in the gaseous phase can't get close enough to form a bond with the surface so a monolayer is all you get. Layers can be physically adsorbed on top of the monolayer but they are held by weak intermolecular forces.