K_H value for some gases at the same temperature 'T' are given: where K_H is Henry's Law constant in water. The order of their solubility in water is:

$\displaystyle \mathrm{K}_{\mathrm{H}}$ value for some gases at the same temperature 'T' are given:

Gas	$\displaystyle \mathrm{K}_{\mathrm{H}} / \mathrm{k}$ bar
Ar	$\displaystyle 40.3$
$\displaystyle \mathrm{CO}_2$	$\displaystyle 1.67$
HCHO	$\displaystyle 1.83 \times 10^{-5}$
$\displaystyle \mathrm{CH}_4$	$\displaystyle 0.413$

where $\displaystyle \mathrm{K}_{\mathrm{H}}$ is Henry's Law constant in water. The order of their solubility in water is: