1. What is Relative Lowering of Vapour Pressure?

Definition: The Relative Lowering of Vapour Pressure is the ratio of the decrease in vapour pressure of the solvent to the vapour pressure of the pure solvent.

Purpose: It helps in understanding how adding a solute affects the vapour pressure of a solvent, which is important in colligative properties studies.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta p \) — Relative Lowering of Vapour Pressure (unitless)
• \( p_o \) — Vapour Pressure of Pure Solvent (Pascals)
• \( p \) — Vapour Pressure of Solvent in Solution (Pascals)

Explanation: The difference between pure solvent's vapour pressure and solution's vapour pressure is divided by the pure solvent's vapour pressure.

3. Importance of Relative Lowering of Vapour Pressure

Details: This measurement is crucial for determining molecular weights of solutes and understanding solution behavior in various chemical processes.

4. Using the Calculator

Tips: Enter the vapour pressure values in Pascals. The solution's vapour pressure must be less than the pure solvent's vapour pressure.

5. Frequently Asked Questions (FAQ)

Q1: What does a relative lowering of 0.5 mean?
A: It means the vapour pressure of the solvent in solution is half that of the pure solvent.

Q2: Can the relative lowering be greater than 1?
A: No, it's always between 0 and 1 since p must be less than p₀ but can't be negative.

Q3: What units should I use for vapour pressure?
A: The calculator uses Pascals, but the result is unitless as it's a ratio.

Q4: How does temperature affect this calculation?
A: Temperature affects the vapour pressure values but not the relative lowering calculation method.

Q5: What's a typical value for relative lowering?
A: For dilute solutions, it's typically small (0.01-0.1), increasing with solute concentration.