For a fixed volume of liquid solvent, the solubility of a gaseous solute depends upon.......
(A) Nature of the gas.
(B) Pressure at constant temperature.
(C) Temperature at constant pressure.
(D) Nature of solvent.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B), (C) and (D)
When a gas dissolves in a liquid, gas molecules and dissolved molecules reach a dynamic equilibrium. The position of this equilibrium, and so the solubility, depends on the nature of the gas and the solvent, on the pressure and on the temperature. Henry’s law puts the pressure and the nature of the system together:
\( \displaystyle p = K_H\,x \)
where x is the mole fraction of the gas in solution and \( K_H \), Henry’s law constant, depends on the gas, the solvent and the temperature.
(A) Nature of the gas. — Correct. Different gases have different \( K_H \) values in water at the same temperature (\( \ce{O2} \) 34.86 kbar, He 144.97 kbar at 293 K), and a gas that reacts with the solvent, such as \( \ce{NH3} \) or HCl in water, is far more soluble.
(B) Pressure at constant temperature. — Correct. At a fixed temperature the solubility is directly proportional to the partial pressure of the gas; this is why soft drinks are bottled under high pressure of \( \ce{CO2} \).
(C) Temperature at constant pressure. — Correct. Dissolution of a gas is exothermic, so the solubility falls as the temperature rises; \( K_H \) increases with temperature. Aquatic life is more comfortable in cold water, which holds more oxygen.
(D) Nature of solvent. — Correct. The same gas has different solubilities in different solvents; HCl, for example, is very soluble in water but much less so in cyclohexane.
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – “Many gases dissolve in water. Oxygen dissolves only to a small extent in water. It is this dissolved oxygen which sustains all aquatic life. On the other hand, hydrogen chloride gas (HCl) is highly soluble in water. Solubility of gases in liquids is greatly affected by pressure and temperature. The solubility of gases increase with increase of pressure.”