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Give information about the type of adsorption. |
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Answer» Solution :There are mainly two types of adsorption of gases on solids. If accumulation of gas on the surface of a solid occurs on account of weak van der Waals. forces, the adsorption is termed as physical adsorption or PHYSISORPTION. When the gas molecules or ATOMS are held to the solid surface by chemical bonds the adsorption is termed as chemical adsorption or chemisorption. The chemical bonds may be covalent or ionic in nature. Chemisorption involves a high energy of ACTIVATION and is ALSO often referred to as activated adsorption. Sometimes these two processes occurs simultaneously and it is not easy to ascertain the type of adsorption. A physical adsorption at low temperature may pass into chemisorption as the temperature is INCREASED. For example, dihydrogen is first adsorbed on nickel by van der Waals. forces. Molecules of hydrogen then dissociate to form hydrogen atoms which are held on the surface by chemisorption. |
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