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 calculation helps in understanding colligative properties of solutions and is important in chemical engineering and physical chemistry.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta p \) — Relative Lowering of Vapour Pressure
• \( i \) — Van't Hoff Factor
• \( n \) — Number of Moles of Solute (mol)
• \( N \) — Number of Moles of Solvent (mol)

Explanation: The Van't Hoff factor accounts for the number of particles the solute dissociates into, while the mole ratio determines the relative effect on vapour pressure.

3. Importance of Vapour Pressure Calculation

Details: Understanding vapour pressure lowering is crucial for predicting boiling point elevation, freezing point depression, and osmotic pressure of solutions.

4. Using the Calculator

Tips: Enter the Van't Hoff factor (default 1.008 for non-electrolytes), moles of solute, and moles of solvent (default 10). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the Van't Hoff factor?
A: It's the ratio of observed colligative property to theoretical colligative property, accounting for solute dissociation.

Q2: What's a typical Van't Hoff factor value?
A: For non-electrolytes it's 1, for strong electrolytes it's the number of ions produced (e.g., 2 for NaCl).

Q3: Why is relative lowering important?
A: It's a fundamental colligative property that helps determine solution behavior regardless of solute nature.

Q4: How do I find the number of moles?
A: Moles = mass (g) / molar mass (g/mol). Use our Molar Mass Calculator if needed.

Q5: Does this work for concentrated solutions?
A: This formula works best for dilute solutions. For concentrated solutions, activity coefficients must be considered.