Surface Chemistry

Chemisorption refers to the process in which a gas molecule chemically bonds with a surface. The key characteristics of chemisorption are: - **(1) It is endothermic in nature:** Chemisorption typically requires energy to break bonds and form new ones, hence it is endothermic. - **(2) The extent of chemisorption first increases with temperature, then decreases:** Chemisorption increases with temperature up to an optimal point. At very high temperatures, the adsorbed molecules may desorb due to the increased kinetic energy. - **(3) Enthalpy of adsorption is in the range of 40-400 kJ/mol:** This is correct because chemisorption involves the formation of strong chemical bonds, leading to high enthalpy values. - **(4) It is reversible in nature:** This statement is incorrect. Chemisorption is typically irreversible due to the strong chemical bonds formed during the process. Thus, the incorrect statement is (4). Final Answer: