COMPARISON OF PHYSICAL ADSORPTION AND CHEMISORPTION
1. Caused by intermolecular van der Waal’s
2. Depends on nature of gas. Easily liquefiable
gases are adsorbed readily.
3. Heat of adsorption is small (about 5 kcal
5. Occurs rapidly at low temperature; decreases
with increasing temperature.
6. Increase of pressure increases adsorption;
decrease of pressure causes desorption.
7. Forms multimolecular layers on adsorbent
In chemisorption, the adsorbed layer of gas is one-molecule thick since chemical combination
1. Caused by chemical bond formation.
2. Much more specific than physical
3. Heat of adsorption is large (20–100 kcal
5. Increases with increase of temperature.
6. Change of pressure has no such effects.
7. Forms unimolecular layer.