Which statement is not true for physisorption ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Chemical bond is responsible.
In physisorption (physical adsorption) the adsorbate is held on the surface by weak van der Waals forces, not by chemical bonds. A chemical bond between adsorbate and adsorbent is the feature of chemisorption. So the statement “Chemical bond is responsible” is not true for physisorption.
Option (1) It is not specific in nature. — True for physisorption. Van der Waals forces are universal.
Option (2) It is reversible in nature. — True for physisorption. A gas adsorbed at high pressure is released when the pressure is lowered.
Option (3) Enthalpy of adsorption is low. — True for physisorption. It is about 20–40 kJ mol−1.
Option (4) Chemical bond is responsible. — Not true for physisorption. It is the feature of chemisorption.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Types of Adsorption – …
