Question

Which statement is not true for physisorption?

• A. It is not specific in nature.
• B. It is reversible in nature.
• C. Enthalpy of adsorption is low.
• D. Chemical bond is responsible.

Answer 1

The Correct Option is D

To determine which statement is not true for physisorption, we must consider the characteristics of physisorption:

• Non-specific in nature: Physisorption, or physical adsorption, occurs due to weak van der Waals forces and can happen on any kind of surface.
• Reversible in nature: Because the forces involved are weak, physisorption can be easily reversed by changing conditions like pressure or temperature.
• Low enthalpy of adsorption: The process involves weak interactions, so the enthalpy of adsorption is low, typically in the range of 20-40 kJ/mol.
• Not due to chemical bonds: Physisorption does not involve the formation of new chemical bonds, unlike chemisorption, which involves chemical bonding.

Given the options and the characteristics listed, the statement "Chemical bond is responsible" is not true for physisorption. Therefore, this option correctly identifies the incorrect statement about physisorption.

Answer 2

Physisorption is a type of adsorption that involves the physical attachment of molecules to the surface of a solid or liquid. This process does not involve the formation of chemical bonds; instead, the interaction is primarily due to van der Waals forces, which are weak intermolecular forces. Physisorption typically occurs at lower temperatures and results in a reversible attachment, meaning that the adsorbed molecules can easily desorb from the surface.

In contrast, chemisorption involves the formation of chemical bonds between the adsorbate and the surface, resulting in a much stronger interaction. Chemisorption is usually specific to certain molecules and can lead to the formation of stable, irreversible bonds. This type of adsorption occurs at higher temperatures and often requires activation energy to break the molecular bonds of the adsorbate.

In summary, while both physisorption and chemisorption are important in various applications, such as catalysis and surface chemistry, the key difference lies in the nature of the interaction: physisorption relies on weak van der Waals forces, while chemisorption involves the formation of chemical bonds.