MHTCET 26 Apr 2025 Shift 1 Paper

Concept: The extent of physical adsorption of a gas on a solid increases with its ease of liquefaction, which is directly related to its critical temperature. Gases with lower critical temperatures are adsorbed less.Explanation:Adsorption of gases on solids depends on intermolecular forces between gas molecules and the solid surface. Gases that are easy to liquefy (higher critical temperature) have stronger van der Waals forces and adsorb more readily. Critical temperature ($T_c$) is the temperature above which a gas cannot be liquefied by pressure alone. Higher $T_c$ means greater ease of liquefaction and therefore greater adsorption. Among the given gases: $\mathrm{Cl}_{2}$ ($T_c \approx 144^\circ\mathrm{C}$), $\mathrm{SO}_{2}$ ($T_c \approx 157^\circ\mathrm{C}$), $\mathrm{NH}_{3}$ ($T_c \approx 132^\circ\mathrm{C}$), and $\mathrm{H}_{2}$ ($T_c \approx -240^\circ\mathrm{C}$). Clearly, $\mathrm{H}_{2}$ has the lowest critical temperature among these gases. Thus, $\mathrm{H}_{2}$ is the least adsorbed on a solid at similar conditions of temperature and pressure.Answer: D. $\mathrm{H}_{2}$