Which principle states that the partial vapour pressure of each volatile component in a solution is directly proportional to its mole fraction?

The correct answer is Raoult's Law.

Key Points

• Raoult's Law states that the partial vapour pressure of each component in a solution is directly proportional to its mole fraction in the liquid phase.
• The law is expressed as P_A = X_A * P_A°, where P_A is the partial pressure of component A, X_A is its mole fraction, and P_A° is its vapour pressure in pure state.
• Raoult's Law is applicable to ideal solutions, where interactions between different molecules are similar to those between like molecules.
• This principle helps in determining the composition of vapour and liquid phases in equilibrium in mixtures.
• It is widely used in fields like chemical engineering and physical chemistry for processes such as distillation and evaporation.

Additional Information

• Henry's Law: States that the amount of gas dissolved in a liquid is proportional to its partial pressure above the liquid. This law is useful in understanding solubility of gases in liquids.
• Dalton's Law: Describes the relationship where the total pressure of a gas mixture is the sum of the partial pressures of individual gases. It is critical in calculating gas pressures in mixtures.
• Boyle's Law: States that the pressure of a gas is inversely proportional to its volume at constant temperature. It is applicable to ideal gases in closed systems.
• Ideal Solution: A solution that follows Raoult's Law exactly and exhibits uniform molecular interactions, with no energy changes upon mixing.
• Vapour Pressure: The pressure exerted by a substance in its gaseous phase when in equilibrium with its liquid or solid phase at a given temperature.