Relative Lowering of Vapour Pressure given Weight and Molecular Mass of Solute and Solvent Calculator

Relative Lowering of Vapour Pressure Formula:

\[ Δp = \frac{w \times M}{W \times M_{solute}} \]

Weight of Solute:

Molecular Mass Solvent:

Weight of Solvent:

Molecular Mass Solute:

Relative Lowering of Vapour Pressure (Δp):

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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: 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:

\[ Δp = \frac{w \times M}{W \times M_{solute}} \]

Where:

\( Δp \) — Relative Lowering of Vapour Pressure
\( w \) — Weight of Solute (kg)
\( M \) — Molecular Mass of Solvent (kg)
\( W \) — Weight of Solvent (kg)
\( M_{solute} \) — Molecular Mass of Solute (kg)

Explanation: The formula relates the weights and molecular masses of solute and solvent to the change in 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.

4. Using the Calculator

Tips: Enter the weight of solute, molecular mass of solvent (default 0.018 kg for water), weight of solvent (default 0.02 kg), and molecular mass of solute (default 0.035 kg). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What units should I use for input?
A: All weights should be in kilograms (kg) and molecular masses in kg/mol (but entered as kg in this calculator).

Q2: Why is the default solvent mass 0.018 kg?
A: This represents the molecular mass of water (18 g/mol converted to kg).

Q3: What does the result represent?
A: The result is a dimensionless ratio showing how much the vapour pressure is reduced compared to the pure solvent.

Q4: Can I use this for non-ideal solutions?
A: This formula works best for ideal solutions. For non-ideal solutions, activity coefficients should be considered.

Q5: How precise should my measurements be?
A: For accurate results, measure weights to at least 4 decimal places (in kg) as these are typically small quantities.