Question

Which of the following is/are true for physisorption?

• A. Easily liquefied gases are more adsorbed.
• B. Weak van der Waals forces cause the adsorption process.
• C. Only unimolecular layer formation.
• D. Adsorbtion increases with rise in temperature.

Answer 1

Answer: (A), (B)

The correct options are
A Easily liquefied gases are more adsorbed.
B Weak van der Waals forces cause the adsorption process.

1. Physisorption is the physical bonding of gas molecules to the surface of a solid or liquid that the gas comes into contact with at low temperatures. This occurs due to Van der Waals forces. The weak, long-range bonding is not surface specific and takes place between all gas molecules on any surface. The process, which does not involve any surface reaction, is achieved quickly at low temperatures, but surface coverage reduces with temperature increase. Physisorption is used when measuring the total surface area and in pore size analysis of mesopores, micropores and nanopores.

   Physisorption is also known as physical adsorption.

2. Hence options A & B are correct.