Question

Which of the following statements is not correct for chemisorption and physisorption?

• A. Physical adsorption occurs at a low temperature and chemisorption occurs at high temperatures.
• B. Magnitude of chemisorption decreases with rise in temperature while physisorption increases with rise in temperature.
• C. Chemisorption is irreversible and physisorption is reversible.
• D. In physisorption activation energy is low while in chemisorption it is high.

Answer 1

The correct option is B Magnitude of chemisorption decreases with rise in temperature while physisorption increases with rise in temperature.

• Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface.
• If the accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption.
• The chemical bonds may be covalent or ionic in nature. Chemisorption involves a high energy of activation and is, therefore, often referred to as activated adsorption.
• Hence, a physical adsorption at low temperature may pass into chemisorption as the temperature is increased.
• So, the magnitude of chemisorption increases with rising in temperature while physisorption decreases with rising in temperature.