Solubility, Henry's Law, and Raoult's Law

Decide whether the question is about a gas dissolved in a liquid or a volatile liquid mixture. Use Henry's law for gas solubility under pressure. Use Raoult's law when vapour pressure and mole fraction of liquid components are involved. Substitute pressure units consistently and interpret whether solubility or vapour pressure increases or decreases.

A pressure-solubility graph can support Henry's law, but it is not mandatory for this concept. A straight-line relation at constant temperature is enough for most questions.

Using p = p^0 x for gas solubility instead of Henry's law is a realistic formula-selection error.

Henry's law relates the solubility of a gas in a liquid to its partial pressure, while Raoult's law relates the vapour pressure of a volatile component in an ideal solution to its mole fraction.

Henry's law relates the solubility of a gas in a liquid to its partial pressure, while Raoult's law relates the vapour pressure of a volatile component in an ideal solution to its mole fraction. Henry's law: p = K_H x for a gas dissolved in a liquid. Raoult's law for an ideal solution: p_i = p_i^0 x_i. Total pressure for two volatile components: p_total = p_A^0 x_A + p_B^0 x_B. Carbonated drinks are bottled under high CO₂ pressure, so more CO₂ remains dissolved. When the bottle is opened, pressure decreases and CO₂ escapes.

For gases dissolved in liquids, higher pressure generally increases solubility at a fixed temperature. Henry's law is commonly written as p = K_H x, where x is mole fraction of gas in solution; some simplified contexts express solubility as directly proportional to pressure. Raoult's law states that the partial vapour pressure of a component equals its pure vapour pressure multiplied by its mole fraction in the solution. Henry's law: p = K_H x for a gas dissolved in a liquid. Raoult's law for an ideal solution: p_i = p_i^0 x_i. Total pressure for two volatile components: p_total = p_A^0 x_A + p_B^0 x_B. If p_A^0 = 80 kPa, p_B^0 = 50 kPa, x_A = 0.30, and x_B = 0.70 for an ideal solution, then p_total = 80 x 0.30 + 50 x 0.70 = 24 + 35 = 59 kPa. Interpretation: the vapour pressure is the mole-fraction-weighted sum of partial pressures. Questions often ask for gas solubility trends with pressure, applications such as soda bottles or deep-sea diving, calculation of vapour pressure using Raoult's law, or assertion-reason links between pressure and gas dissolution. Using p = p^0 x for gas solubility instead of Henry's law is a realistic formula-selection error.