Difference between Physisorption and Chemisorption

Physisorption and Chemisorption

The adsorption is the process in which molecules of substance get accumulated on the surface of another substance due to unbalanced attractive forces. On the basis of the forces involved in adsorption, there are two types – physical adsorption and activated (chemical) adsorption

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Physisorption ( physical adsorption ) Chemisorption ( activated adsorption )
It involves physical or Van der Waal’s forces between absorbate and adsorbent.It involves the formation of chemical or covalent bonds between adsorbate and adsorbent.
The heat of adsorption is low about 20 to 40 KJ per mole of an adsorbate, The heat of adsorption is high about 40 to 220 KJ per mole of an adsorbate,
It involves the formation of multilayers of adsorbate molecules on the surface of the adsorbent. It involves the formation of a monolayer of adsorbate molecules on the surface of the adsorbent.
It occurs at low temperature and extent of adsoprtion decreases as temperature increases.It occurs at all temperature but the rate of adsorption increases as temperature increases.
This is a reversible process as desorption of adsorbed molecules take place on heating.This is an irreversible process as desorption of adsorbed molecules do not take place on heating.
It does not involve activation energy.
It involves activation energy.
It is relatively weak and not specific in nature It is relatively strong and specific in nature

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