The increasing order of solubility in water at 298 K, of the following gases is
(A) Carbon dioxide (KH = 1.67 kbar)
(B) Vinyl chloride (KH = 0.611 kbar)
(C) Methane (KH = 0.413 kbar)
(D) Formaldehyde (KH = 1.83 x 10-5 kbar)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B), (C), (D)
By Henry’s law, the partial pressure of a gas above a solution is proportional to its mole fraction in the solution:
\( \displaystyle p=K_H\,x\quad\Rightarrow\quad x=\frac{p}{K_H} \)
At the same pressure and temperature, the higher the KH, the lower the solubility of the gas. So solubility follows the reverse of the KH order.
KH values at 298 K, from highest to lowest:
\( \displaystyle \ce{CO2}\ (1.67) > \text{vinyl chloride}\ (0.611) > \ce{CH4}\ (0.413) > \ce{HCHO}\ (1.83\times10^{-5})\ \mathrm{kbar} \)
Solubility therefore increases in the opposite direction:
\( \displaystyle \ce{CO2} < \text{vinyl chloride} < \ce{CH4} < \ce{HCHO} \)
\( \displaystyle \text{(A)} < \text{(B)} < \text{(C)} < \text{(D)} \)
Shortcut: Formaldehyde has by far the smallest KH, so it is the most soluble and must come last. Only Option (3) ends with (D).
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – …
