A gas that is readily adsorbed on 1 g of activated charcoal by physical adsorption
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Sulphur Dioxide (critical temperature 630 K)
Arranging the given gases by critical temperature:
\( \ce{SO2} \) (630 K) > \( \ce{CH4} \) (190 K) > \( \ce{H2} \) (33 K) > He (2.15 K)
The extent of adsorption falls in the same order, so sulphur dioxide is the most readily adsorbed.
Why the other options are incorrect
Option (1) Dihydrogen (critical temperature 33 K) — Incorrect. A very low critical temperature; it is hard to liquefy and only a small volume is adsorbed.
Option (2) Helium (critical temperature 2.15 K) — Incorrect. The lowest critical temperature of the four, so it is adsorbed least.
Option (3) Methane (critical temperature 190 K) — Incorrect. Adsorbed more than \( \ce{H2} \), but much less than \( \ce{SO2} \).
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):
Characteristics of Physisorption – …
