Physical   Absorption
            
            

            
Chemical   Absorption
            
        
        

            

            
1)        Caused by intermolecular van der waal’s forces.
            
            

            
Caused by chemical bond formation
            
        
        

            

            
2)        Depends on nature of gas. Easily liquefiable   gases are adsorbed readily.
            
            

            
Much more specific and depends upon the nature of both the adsorbate   and adsorbent.
            
        
        

            

            
3)        Heat of adsorption is small
            
            

            
Very large heat of adsorption
            
        
        

            

            
4)        It is reversible
            
            

            
It is irreversible
            
        
        

            

            
5)        Forms multimolecular layers on adsorbent   surface.
            
            

            
Forms unimolecular layer.
            
        
        

            

            
6)        Occurs at low temperature; decreases with increase   in temperature
            
            

            
Increase with increase of temperature.
            
        
        

            

            
7)        Increase of pressure increases adsorption.
            
            

            
High pressure is favourable. Decrease of pressure does not cause   desorption.
            
        
        

            

            
8)        Equilibrium is attained readily and it is   reversible.
            
            

            
Equilibrium is attained slowly and mostly not reversible.
            
        
    

										

										
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