Passage:
Solubility of gases in liquids is greatly affected by pressure and temperature. Henry gave the quantitative relationship between pressure and solubility of gas in a solvent. According to Henry’s law, partial pressure of a gas above a liquid is directly proportional to its mole fraction in solution and is expressed as \(P = K_H.x\), where \(K_H\) is Henry’s constant and x is mole fraction of gas. \(K_H\) is a function of nature of gas.
F M Raoult gave a quantitative relationship between partial pressures and mole fractions in the binary solution of volatile liquids. Raoult’s law states that for a binary solution of volatile liquids, the partial pressure of each component in the solution is directly proportional to its mole fraction. Thus for a solution of component \(1\) and \(2\), partial pressure of each component \(P_1 = p_1^0x_1\), where \(p_1^0\) is the vapour pressure of pure component \(1\) at the same temperature. Similarly \(P_2 = p_2^0x_2\)
Solubility of Carbon dioxide in soda water increases with
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Increase in pressure and decrease in temperature
The solubility of a gas in a liquid depends on pressure and on temperature:
Pressure: by Henry’s law (p = KHx), the mole fraction of a gas in solution is proportional to its partial pressure above the solution. Higher pressure pushes more gas molecules into the liquid, so solubility increases with pressure.
Temperature: dissolving a gas is like condensing it, so the process is exothermic. By Le Chatelier’s principle, a rise in temperature shifts the equilibrium back towards the gas, so solubility decreases with rise in temperature (KH increases with temperature).
\( \displaystyle \ce{CO2(g) <=> CO2(aq)} \qquad \Delta H \lt 0 \)
So the solubility of \( \ce{CO2} \) in soda water increases with an increase in pressure and a decrease in temperature. That is why soda bottles are sealed under high pressure and fizz more when warm.
NCERT (2026-27 edition):
Effect of Temperature
