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Which is not correct regarding the adsorption of a gas on surface of solid: -
A
On increasing temp. adsorption increases continuously
B
Enthalpy and entropy changes are –ve
C
Adsorption is more for some specific substances
D
Reversible
Detailed Solution
Adsorption is exothermic ($\Delta H$ negative). The gas molecules become more ordered on the surface, so $\Delta S$ is also negative. Correct.
Physical adsorption is reversible; and adsorption is more for some gases (easily liquefiable ones) and on some specific surfaces. Correct.
Since adsorption is exothermic, by Le Chatelier's principle it decreases with increase in temperature (physisorption decreases steadily; chemisorption first increases and then decreases). It does not increase continuously.
So the statement that is not correct is: on increasing temperature, adsorption increases continuously.
Physical adsorption is reversible; and adsorption is more for some gases (easily liquefiable ones) and on some specific surfaces. Correct.
Since adsorption is exothermic, by Le Chatelier's principle it decreases with increase in temperature (physisorption decreases steadily; chemisorption first increases and then decreases). It does not increase continuously.
So the statement that is not correct is: on increasing temperature, adsorption increases continuously.