Which one of the following statements is correct with reference to the solubility of gases in liquid?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → The solubility of gases in liquids increases with the increase of pressure.
When a gas dissolves, a dynamic equilibrium is set up between gas molecules in the vapour phase and those in the solution. If the pressure is raised, more molecules strike the liquid surface and enter it, until a new equilibrium with more dissolved gas is reached. This is expressed by Henry’s law: at a constant temperature, the solubility of a gas is directly proportional to its partial pressure, \( p = K_H\,x \).
So the solubility of gases in liquids increases with the increase of pressure.
Why the other options are incorrect
Option (2) The solubility of gases in liquids is not affected with the increase of temperature. — Incorrect. Temperature does affect it: dissolving a gas is an exothermic process, so by Le Chatelier’s principle the solubility decreases as the temperature rises (\( K_H \) increases with temperature).
Option (3) The solubility of gases in liquids increases with the increase of temperature. — Incorrect. It is the reverse; this is why aquatic animals are more comfortable in cold water, which holds more dissolved oxygen.
Option (4) At high altitude, the partial vapour pressure of \(O_2\) becomes greater than that at the sea level. — Incorrect. The atmospheric pressure falls with height, so the partial pressure of oxygen at high altitude is lower, which is the cause of anoxia in climbers.
NCERT (2026-27 edition):
Solubility of a Gas in a Liquid – “… Henry was the first to give a quantitative relation between pressure and solubility of a gas in a solvent which is known as Henry’s law. The law states that at a constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas present above the surface of liquid or solution.”
“… Solubility of gases in liquids decreases with rise in temperature.”