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(a) Adsorption of a gas on the surface of solid is generally accompanied by a decrease in entropy. Still it is a spontaneous process. Explain. (b) How does an increase in temperature affect both physical as well as chemical adsorption? |
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Answer» SOLUTION : (a) ACCORDING to the equation `DELTAG=DeltaH_T DeltaS ` For a process to be spontaneous, `DeltaG` should be negative.` DELTAH` of adsorption is always negative. For a gas, `DeltaS` is also negative. Thus, in an adsorption process, which is spontaneous, a combination of these two factors always makes `DeltaG` negative. (b) On increasing the temperature desorption occurs in case of physical adsorption. CHEMICAL adsorption first increases and then decreases with increase in temperature. |
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