Question

Explain the term chemisorption.

Answer 1

Chemisorption, or chemical adsorption, is the process where gas molecules attach to the surface of a solid adsorbent by forming strong chemical bonds, such as valence bonds. Unlike physical adsorption which relies on weak van der Waals forces, chemisorption involves specific and strong interactions, making it highly specific and usually irreversible. It typically forms only a single monolayer of adsorbed molecules because once the surface atoms are bonded, no further layers can form. Chemisorption also releases more heat (higher enthalpy) compared to physical adsorption. The extent of chemisorption varies with temperature; it increases initially due to activation energy requirements and then decreases at higher temperatures. Finally, it increases with pressure because higher pressure brings gas molecules closer to the surface to form bonds. Overall, chemisorption behaves more like a chemical reaction between the adsorbate and adsorbent surface rather than simple physical attraction.