1. What is Relative Lowering of Vapour Pressure?

Definition: The Relative Lowering of Vapour Pressure is the lowering of vapour pressure of pure solvent on addition of solute.

Purpose: This calculator helps determine how much the vapour pressure of a solvent decreases when a non-volatile solute is added, based on osmotic pressure measurements.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta p \) — Relative Lowering of Vapour Pressure
• \( \pi \) — Osmotic Pressure (Pascal)
• \( V_m \) — Molar Volume (m³/mol)
• \( [R] \) — Universal gas constant (8.314 J/mol·K)
• \( T \) — Temperature (Kelvin)

Explanation: The formula relates the osmotic pressure of a solution to the relative lowering of its vapour pressure through thermodynamic principles.

3. Importance of This Calculation

Details: Understanding vapour pressure lowering is crucial for studying colligative properties, designing distillation processes, and predicting solution behavior.

4. Using the Calculator

Tips: Enter the osmotic pressure in Pascals, molar volume in m³/mol, and temperature in Kelvin. The temperature defaults to 298K (25°C).

5. Frequently Asked Questions (FAQ)

Q1: What is the physical significance of relative lowering of vapour pressure?
A: It measures how much a solute affects the solvent's tendency to evaporate, important for understanding solution properties.

Q2: What are typical values for molar volume?
A: For water at 25°C, molar volume is about 1.8×10⁻⁵ m³/mol, but this varies with substance and temperature.

Q3: Why is temperature important in this calculation?
A: Temperature affects both the osmotic pressure and the vapour pressure, so it's a critical variable in the relationship.

Q4: Can this calculator be used for any solvent?
A: Yes, as long as you have the correct molar volume for your solvent at the given temperature.

Q5: How accurate is this calculation?
A: It's theoretically exact for ideal solutions, but real solutions may show deviations due to intermolecular interactions.