JEE Main 2025 Apr 2 Shift 1, Chemistry Q4: Vapour Pressure Of A Solution

Henry's law constant $K_H$ is inversely related to gas solubility. The solubility of most gases in water first decreases with rising temperature (gas escapes as kinetic energy grows), then increases at higher temperatures for some gases due to changing hydration behaviour. Consequently $K_H$ first increases and then decreases, producing a curve with a maximum.

At moderate temperatures the magnitude of $K_H$ reflects how poorly soluble the gas is. Among the species in the options, the ordering of $K_H$ is:

$$\text{He}>N_2>C{H}_4$$

$\therefore$ The graph that shows three peaked curves with He highest, $N_2$ in the middle and $C{H}_4$ lowest matches option (4).