Consider the following statements about the solubility of gases in liquids.
(A) Different gases have different values of the Henry’s law constant (KH) at the same temperature, which shows that KH is a function of the nature of the gas.
(B) At a given pressure, the higher the value of KH, the higher is the solubility of the gas in the liquid.
(C) The KH values of both N2 and O2 in water increase with increase of temperature.
(D) The dissolution of a gas in a liquid can be considered similar to evaporation, and heat is absorbed in this process.
Which of the statements given above are incorrect? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) and (D) only
Henry’s law, p = KHx, gives the mole fraction of a dissolved gas as x = p/KH. At a fixed partial pressure, a larger KH means a smaller x, that is, a less soluble gas.
(A) Different gases have different values of the Henry’s law constant (KH) at the same temperature, which shows that KH is a function of the nature of the gas. — Correct statement. At 293 K, for example, KH is 144.97 kbar for He and 34.86 kbar for O2.
(B) At a given pressure, the higher the value of KH, the higher is the solubility of the gas in the liquid. — Incorrect statement. Since x = p/KH, a higher KH gives a lower solubility.
(C) The KH values of both N2 and O2 in water increase with increase of temperature. — Correct statement. KH of N2 rises from 76.48 kbar at 293 K to 88.84 kbar at 303 K, and that of O2 from 34.86 to 46.82 kbar. So both gases dissolve less in warmer water.
(D) The dissolution of a gas in a liquid can be considered similar to evaporation, and heat is absorbed in this process. — Incorrect statement. Dissolved gas molecules pass into the liquid phase, so the process is like condensation, and heat is evolved. Being exothermic, it gives a lower solubility at a higher temperature.
NCERT (2026-27 edition):
1.3.2 Solubility of a Gas in a Liquid – “Different gases have different KH values at the same temperature (Table 1.2). This suggests that KH is a function of the nature of the gas.”
“It is obvious from equation (1.11) that higher the value of KH at a given pressure, the lower is the solubility of the gas in the liquid. It can be seen from Table 1.2 that KH values for both N2 and O2 increase with increase of temperature indicating that the solubility of gases increases with decrease of temperature.”
\( \displaystyle p = K_H\,x \qquad (1.11) \)
“Solubility of gases in liquids decreases with rise in temperature. When dissolved, the gas molecules are present in liquid phase and the process of dissolution can be considered similar to condensation and heat is evolved in this process.”
Table 1.2: Values of Henry’s Law Constant for Some Selected Gases in Water
