Answer the questions based on the passage given below:
Adsorption is a surface phenomenon and it differs from absorption which occurs throughout the body of the substance that absorbs. In physisorption the attractive forces are mainly van der Waals forces while in chemisorption ionic / covalent bonds are formed between particles of adsorbent and adsorbate. The catalytic activity of finely divided iron in Haber's process of ammonia manufacture can be explained by adsorption theory. Adsorption being an exothermic process, the heat of adsorption is utilized in enhancing the rate of the reaction. Adsorption has many applications being used in gas masks, control of humidity, chromatograph separation, curing diseases etc.
Chromatography is based on:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Physical adsorption
In chromatography the components of a mixture are adsorbed to different extents on a stationary phase (alumina, silica gel, paper) and are then washed off one by one by the moving solvent. The adsorption is weak and reversible (van der Waals forces), which is what lets each component be taken off the adsorbent again. That is physical adsorption.
Why the other options are incorrect
Option (2) Chemical adsorption — Incorrect. Chemisorption forms chemical bonds and is usually irreversible, so the components could not be eluted and separated.
Option (3) Homogeneous catalysis — Incorrect. No reaction is catalysed in chromatography; it is only a separation.
Option (4) Heterogeneous catalysis — Incorrect. Again, nothing is catalysed; the adsorbent only holds the components back for different times.
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):
Applications of Adsorption – …
