There are several examples, which reveal that the surface of a solid has the tendency to attract and retain the molecules of the phase with which it comes into contact. These molecules remain only at the surface and do not go deeper into the bulk. The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption. The molecular species or substance, which concentrates or accumulates at the surface is termed adsorbate and the material on the surface of which the adsorption takes place is called adsorbent.

Adsorption is essentially a surface phenomenon. Solids, particularly in finely divided state, have large surface area and therefore, charcoal, silica gel, alumina gel, clay, colloids, metals in finely divided state, etc. act as good adsorbents.

Which of the following statements is not true with respect to chemisorption?

Occurs at low temperature

Chemisorption is a type of adsorption in which the adsorbent and adsorbate undergo a chemical reaction that creates a chemical bond between them. Chemisorption has a high heat of adsorption and is very dependent on the reactants (adsorbent and adsorbate) due to the need to create a link. Moreover, since bond formation is required, it cannot have several layers. High temperatures are preferred for chemisorption to take place.