Weight of Solvent given Relative Lowering of Vapour Pressure Calculator

Formula Used:

\[ W = \frac{p_o \times w \times M}{(p_o - p) \times M_{solute}} \]

Vapour Pressure of Pure Solvent:

Weight of Solute:

Molecular Mass Solvent:

Vapour Pressure of Solvent in Solution:

Molecular Mass Solute:

Weight of Solvent (kg):

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1. What is Weight of Solvent given Relative Lowering of Vapour Pressure?

Definition: This calculator determines the weight of solvent needed based on the relative lowering of vapour pressure when a solute is added.

Purpose: It helps in understanding colligative properties of solutions and is particularly useful in physical chemistry applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ W = \frac{p_o \times w \times M}{(p_o - p) \times M_{solute}} \]

Where:

\( W \) — Weight of solvent (kg)
\( p_o \) — Vapour pressure of pure solvent (Pa)
\( w \) — Weight of solute (kg)
\( M \) — Molecular mass of solvent (kg)
\( p \) — Vapour pressure of solvent in solution (Pa)
\( M_{solute} \) — Molecular mass of solute (kg)

Explanation: The formula relates the weight of solvent to the change in vapour pressure caused by adding a solute.

3. Importance of This Calculation

Details: Understanding this relationship is crucial for studying colligative properties, designing chemical processes, and predicting solution behavior.

4. Using the Calculator

Tips: Enter all required values in consistent units. Ensure vapour pressure of pure solvent is greater than that in solution.

5. Frequently Asked Questions (FAQ)

Q1: What is relative lowering of vapour pressure?
A: It's the ratio of the decrease in vapour pressure to the original vapour pressure of the pure solvent.

Q2: Why does adding solute lower vapour pressure?
A: Solute particles occupy space at the surface, reducing the number of solvent molecules that can escape into the vapour phase.

Q3: What units should I use?
A: Use consistent units - kg for masses and Pa for pressures. The calculator assumes SI units.

Q4: Can this be used for any solute-solvent pair?
A: This works best for ideal solutions where Raoult's law applies. For non-ideal solutions, activity coefficients are needed.

Q5: What if my vapour pressure in solution is higher than pure solvent?
A: This would indicate an error in measurement, as adding solute should always lower the vapour pressure.