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# Which of the following are correct pertaining to the adsorption of a gas can a solid surface ?

$\begin{array}{1 1} \text{(a) physisorption may transform into chemisorption at high temperature.} \\ \text{(b) chemisorption is more exothermic than physisorption at high temperature. } \\ \text{(c) physisorption increases with increasing temperature but chemisorption decreases with increasing temperature} \\ \text{(d) chemisorption is more endothermic than physisorption.} \end{array}$

Answer : chemisorption is more exothermic than physisorption at high temperature.
Explanation :
Heat is evolved in both physical & chemical adsorption . Further , chemical adsorption leads to the formation of surface compound . The process involved are similar to those of chemical bond . This is confirmed by the fact that heat is evolved during chemisorption are high (200 -400 KJ / mol) while the heat evolved during physisorption is 20 - 40 KJ/mol .