The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. There are two types of adsorption. In physisorption, attractive forces are mainly van der Waals while in chemical adsorption adsorbate is held with chemical bonds adsorbent. Adsorption increases with increase in pressure and decrease as temperature is increased.

Which of the following is not characteristic of chemical adsorption?

It results into multi molecular layers.

 The correct answer is (4) It results into multi molecular layers.

Chemical adsorption is a process in which the adsorbate molecules form chemical bonds with the adsorbent surface. It is a highly specific process, and the adsorbate molecules must have a certain chemical structure in order to adsorb to the adsorbent surface. Chemical adsorption is also irreversible, meaning that the adsorbate molecules cannot be easily removed from the adsorbent surface. High temperature is usually favorable for chemical adsorption, as it provides the energy needed to break the bonds between the adsorbate molecules and the bulk liquid or gas.

The only characteristic of chemical adsorption that is not listed in the options is that it results in multimolecular layers. Chemical adsorption typically results in a unimolecular layer, meaning that only a single layer of adsorbate molecules forms on the adsorbent surface.

Therefore, the answer is (4).