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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.
The calculator uses the formula:
Where:
Explanation: The formula relates the weight of solvent to the change in vapour pressure caused by adding a solute.
Details: Understanding this relationship is crucial for studying colligative properties, designing chemical processes, and predicting solution behavior.
Tips: Enter all required values in consistent units. Ensure vapour pressure of pure solvent is greater than that in solution.
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.