Question

Two open beakers one containing a solvent and the other containing a mixture of that solvent with a non volatile solute are together sealed in a container. Over time:

• A. the volume of the solution and the solvent does not change
• B. the volume of the solution increases and the volume of the solvent decreases
• C. the volume of the solution decreases and the volume of the solvent increases
• D. the volume of the solution does not change and the volume of the solvent decreases

Answer 1

The Correct Option is B

To solve this problem, we need to understand the concept of vapor pressure and how it affects the movement of solvent molecules between the two beakers. Here's a step-by-step explanation:

1. The beaker with just the solvent will have a higher vapor pressure compared to the beaker with the solution that contains a non-volatile solute. This is because adding a non-volatile solute to a solvent results in a decrease in the solvent's vapor pressure (Raoult's Law).
2. The solvent molecules will tend to move from the area of higher vapor pressure (pure solvent) to the area of lower vapor pressure (solution with non-volatile solute) in an attempt to reach equilibrium.
3. This movement of solvent molecules results in the evaporation of the pure solvent and condensation of these molecules into the solution.
4. As more solvent molecules move into the solution, the volume of the solution increases, while the volume of the pure solvent decreases.

Therefore, the correct option is that the volume of the solution increases and the volume of the solvent decreases. This scenario represents the migration of solvent molecules due to differing solvent vapor pressures, aiming to balance the vapor pressure difference by transferring solvent from pure solvent beaker to the solution beaker.