Which of the following gases at 298 K and 1 atm pressure is having maximum solubility in water ?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Methanal, KH = 0.000018
By Henry’s law, p = KH x, so at a given partial pressure the mole fraction of the dissolved gas is
\( \displaystyle x=\frac{p}{K_H} \)
The lower the KH, the higher the solubility. Of the four gases, methanal (formaldehyde) has by far the lowest KH (1.83 × 10−5 kbar), because it is polar and forms hydrogen bonds with water; so it is the most soluble.
Shortcut: Pick the smallest KH.
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – …
