Discuss the characteristics of physical adsorption.

Explanation

Characteristics of physical adsorption :
`to` Lack of specificity : Physisorption is not specific. In this adsorption the given surface of adsorbent doesnot show any preference for a particular gas as the forces present ar vanderwaal's forces (Universal).
Nature of adsorbate : The amount of gas adsorbed by a solid depends on the nature of gas.
`to` Easily liquefiable gases are readily adsorbed.
`to` The gas with high critical temperature value is easily liquified and gets readily adsorbed .
`to` Reversible Nature : Physical adsorption is reversible and occurs rapidly at low temperature .
`to` Surface area of adsorbent : The extent of adsorption increase with increase in surface area of adsorbent.
`to` Finely divided metals and porous substance having large surface area are good adsorbents.
`to` Enthalpy of adosption : Physisorption is an exothermic procress but the enthalpy of adsorption is low (20-40 KJ/mole) . This is due to the presence of Vander waal's forces.