A gas that is readily adsorbed on 1 g of activated charcoal by physical adsorption

Sulphur Dioxide (critical temperature 630 K)

The correct answer is option 4. Sulphur Dioxide (critical temperature 630 K).

The gas that is readily adsorbed on activated charcoal by physical adsorption is (4) Sulphur Dioxide (critical temperature 630 K). Here's why:

Physical adsorption: This type of adsorption involves weak intermolecular forces (van der Waals forces) between the gas molecules and the surface of the adsorbent (activated charcoal).

Role of critical temperature: Generally, gases with higher critical temperatures are more easily adsorbed physically. This is because molecules with higher critical temperatures possess larger van der Waals forces, resulting in stronger interaction with the adsorbent surface.

Analysis of options:

(1) Dihydrogen (critical temperature 33 K): Despite having the lowest critical temperature, dihydrogen molecules are quite small and have weak van der Waals forces, making them less likely to be adsorbed compared to gases with larger molecules and stronger forces.

(2) Helium (critical temperature 2.15 K): Similar to dihydrogen, helium has the lowest critical temperature among all gases and possesses very weak van der Waals forces due to its noble gas configuration. Therefore, it's not readily adsorbed.

(3) Methane (critical temperature 190 K): While having a higher critical temperature than dihydrogen and helium, methane's small molecule size and relatively weak van der Waals forces limit its physical adsorption compared to options with larger molecules and stronger forces.

(3) Sulphur Dioxide (critical temperature 630 K): Among the given options, sulphur dioxide possesses the highest critical temperature, indicating stronger van der Waals forces. Its larger molecule size also contributes to a larger contact area with the adsorbent surface. Therefore, sulphur dioxide is readily adsorbed on activated charcoal by physical adsorption.

Therefore, considering the role of critical temperature and molecule size in physical adsorption, sulphur dioxide is the most likely gas to be readily adsorbed on activated charcoal among the provided options.