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Discuss the characteristics of physical adsorption. |
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Answer» Characteristics of physical adsorption : → 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 are vanderwaal's forces (Universal). → Nature of adsorbate : The amount of gas adsorbed by a solid depends on the nature of gas. → Easily liquefiable gases are readily adsorbed. → The gas with high critical temperature value is easily liquefied and gets readily adsorbed. → Reversible Nature : Physical adsorption is reversible and occurs rapidly at low temperatures. → Surface area of adsorbent : The extent of adsorption increase with increase in surface area of adsorbent. → Finely divided metals and porous substances having large surface area are good adsorbents. → Enthalpy of adsorption : Physisorption is an exothermic process but the enthalpy of adsorption is low (20 - 40KJ/mole). This is due to the presence of Vander waal's forces. |
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