Differentiate between physical and chemical adsorption?

Physical adsorption

It takes places at low temperature and decreases with increase in temperature

Van Der Waals force is the force helding the adsorbate

it is reversible

Not specific

it forms a multimolecular layer

It is dependent of pressure and temperature

examples Clay, silica gel

Chemical Adsorption

It is specific in nature

it involves chemical bonds between the gas molecules and the adsorbent surface

it requires a certain level of energy of activation

The rate of chemical adsorption is directly proportional to the surface area

it forms a unimolecular layer

It is reversible in nature

It is slow at low temperature and occurs at a higher rate with an increase in pressure

example: Rubbing pain balm on the forehead

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