1. What is Mole Fraction of Solute?

Definition: Mole fraction is the ratio of the number of moles of solute to the total number of moles of solute and solvent in a solution.

Purpose: It's a way to express the concentration of a solution and is particularly useful in studying colligative properties like vapour pressure lowering.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( x_{solute} \) — Mole fraction of solute (unitless)
• \( p° \) — Vapour pressure of pure solvent (Pascals)
• \( p \) — Vapour pressure of solvent in solution (Pascals)

Explanation: The difference in vapour pressures is divided by the pure solvent's vapour pressure to determine the solute's mole fraction.

3. Importance of Mole Fraction Calculation

Details: Mole fraction helps predict how much a solute will affect the solvent's properties, particularly its vapour pressure, boiling point, and freezing point.

4. Using the Calculator

Tips: Enter the vapour pressure of pure solvent and the vapour pressure of the solution. Both values must be in Pascals, and solution pressure must be ≤ pure solvent pressure.

5. Frequently Asked Questions (FAQ)

Q1: What does a mole fraction of 0.05 mean?
A: It means 5% of all molecules in the solution are solute molecules (5 solute molecules per 100 total molecules).

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

Q3: What's the range of possible mole fraction values?
A: Mole fraction ranges from 0 (pure solvent) to 1 (pure solute), but typically much less than 1 in real solutions.

Q4: How accurate is this calculation?
A: It's exact for ideal solutions and a good approximation for dilute real solutions.

Q5: Can I use different pressure units?
A: Yes, as long as both pressures are in the same units (mmHg, atm, etc.), the mole fraction will be correct.