Which of the following factors affects the vapor pressure of a liquid according to Raoult's Law?

• A. The presence of a non-volatile solute
• B. The shape of the container
• C. The color of the liquid
• D. The atmospheric pressure above the liquid

Answer: (A)

Verified step by step guidance

1. Understand that Raoult's Law relates the vapor pressure of a solvent in a solution to the presence of solutes, specifically focusing on how solutes affect the escaping tendency of solvent molecules.
2. Recall Raoult's Law formula: \(P_{solution} = X_{solvent} \times P^\circ_{solvent}\), where \(P_{solution}\) is the vapor pressure of the solution, \(X_{solvent}\) is the mole fraction of the solvent, and \(P^\circ_{solvent}\) is the vapor pressure of the pure solvent.
3. Recognize that adding a non-volatile solute decreases the mole fraction of the solvent (\(X_{solvent}\)), which in turn lowers the vapor pressure of the solution compared to the pure solvent.
4. Note that factors like the shape of the container, the color of the liquid, or the atmospheric pressure above the liquid do not directly affect the vapor pressure according to Raoult's Law, as it depends on the composition of the liquid phase.
5. Conclude that the presence of a non-volatile solute is the factor that affects vapor pressure according to Raoult's Law because it changes the mole fraction of the solvent and thus the vapor pressure.