What is reversible adsorption?

Physical adsorption

The correct answer is option 2. Physical adsorption.

Reversible adsorption is: Physical adsorption

Reversible adsorption refers to the process where the adsorbate can be easily removed from the adsorbent by changing the conditions such as temperature or pressure. This is characteristic of physical adsorption.

Physical adsorption (physisorption):

Nature of Forces: Involves weak van der Waals forces.

Reversibility: The adsorbed molecules can easily be desorbed by decreasing the pressure or increasing the temperature, making the process reversible.

Energy Involved: The energy change involved is relatively low, typically in the range of 20-40 kJ/mol.

Example: Adsorption of gases like nitrogen or oxygen on activated charcoal.

Chemical adsorption (chemisorption):

Nature of Forces: Involves the formation of strong chemical bonds between the adsorbate and the adsorbent.

Reversibility: The process is usually irreversible or only reversible with difficulty, as breaking chemical bonds requires significant energy.

Energy Involved: The energy change involved is relatively high, typically in the range of 80-240 kJ/mol.

Example: Adsorption of hydrogen on the surface of a metal catalyst.

Therefore, reversible adsorption is specifically characteristic of physical adsorption due to the weak nature of the forces involved, allowing the adsorbate to be easily removed from the adsorbent.