Question

The enthalpy of chemisorption is ............ than the enthalpy of physisorption.

• A. equal
• B. lesser
• C. greater
• D. none of these

Answer 1

Answer: (C)

greater

The enthalpy of chemisorption is greater than the enthalpy of physisorption.

Chemisorption involves the formation of chemical bonds between the adsorbate and adsorbent, often with a release of heat much larger than the heat of condensation.

It generally takes place at temperatures greater than ${200}^{o}C$ and maybe slow and irreversible.

The heat of physical adsorption is low (1-10 kcal/mol).

The heat of chemical adsorption is high (20-100 kcal/mol).