Vapour Phase Mole Fraction using Modified Raoult's Law in VLE Calculator

Vapour Phase Mole Fraction Formula:

\[ y_{Gas} = \frac{x_{Liquid} \times \gamma_{Raoults} \times P_{sat}}{P_T} \]

Mole Fraction in Liquid Phase (x_Liquid):

Activity Coefficient (γ_Raoults):

Saturated Pressure (P_sat):

Total Pressure (P_T):

Vapour Phase Mole Fraction (y_Gas):

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1. What is Vapour Phase Mole Fraction using Modified Raoult's Law?

Definition: This calculator determines the mole fraction of a component in the vapour phase using Modified Raoult's Law, which accounts for non-ideal behavior in liquid mixtures.

Purpose: It's essential for vapor-liquid equilibrium (VLE) calculations in chemical engineering and thermodynamics.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ y_{Gas} = \frac{x_{Liquid} \times \gamma_{Raoults} \times P_{sat}}{P_T} \]

Where:

\( y_{Gas} \) — Mole fraction in vapour phase
\( x_{Liquid} \) — Mole fraction in liquid phase
\( \gamma_{Raoults} \) — Activity coefficient (accounts for non-ideality)
\( P_{sat} \) — Saturated pressure of the component
\( P_T \) — Total system pressure

Explanation: The formula modifies Raoult's Law by including the activity coefficient to account for deviations from ideal behavior.

3. Importance of Vapour Phase Mole Fraction Calculation

Details: Accurate calculation is crucial for designing distillation columns, flash drums, and other separation processes in chemical industries.

4. Using the Calculator

Tips:

Enter liquid phase mole fraction (0 to 1)
Activity coefficient is 1 for ideal solutions
Ensure consistent pressure units (Pa in this calculator)
Total pressure must be greater than zero

5. Frequently Asked Questions (FAQ)

Q1: What is the activity coefficient?
A: It's a factor that accounts for deviations from ideal solution behavior. γ=1 for ideal solutions, >1 for positive deviations, and <1 for negative deviations.

Q2: When should I use Modified Raoult's Law?
A: Use it for non-ideal liquid mixtures. For ideal mixtures, use standard Raoult's Law (γ=1).

Q3: How do I find the activity coefficient?
A: It can be determined experimentally or calculated using models like Wilson, NRTL, or UNIQUAC equations.

Q4: What if my total pressure is less than saturated pressure?
A: The component would exist as a superheated vapor, and this calculation wouldn't apply.

Q5: Can I use different pressure units?
A: Yes, but ensure all pressure values use the same units for consistent results.