Define absorption. write any two features which distinguish physisorption from chemisorption.

Absorption is the process in which liquid or gas molecules enter bulk of a solid.

Physisorption

• Only van der Waals force are present between adsorbate and surface of adsorbent

• Low enthalpy of adsorption ie, in the order of 20 kjmol-1.
• ​It is usually takes place atlow temperatureand does not require any activation energy.

Chemisorption

• Chemical bonds are formed between adsorbate and surface of adsorbent

• High enthalpy of adsorption i.e,order of 200 kjmol-1.

• It takes place athigh temperatureand require activation energy..