Excess Gibbs Free Energy Formula:
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Definition: Excess Gibbs free energy (Gᴱ) represents the difference between the actual Gibbs free energy of a solution and what it would be if the solution were ideal.
Purpose: The NRTL (Non-Random Two-Liquid) model calculates Gᴱ to predict phase equilibria in non-ideal liquid mixtures.
The NRTL equation calculates excess Gibbs free energy as:
Where:
Details: Gᴱ is crucial for predicting vapor-liquid equilibria, activity coefficients, and phase behavior in non-ideal mixtures.
Tips: Enter mole fractions (must sum to 1), temperature in Kelvin, NRTL coefficients (α, b₁₂, b₂₁). Default values are provided for common systems.
Q1: What are typical values for NRTL parameters?
A: α is usually 0.1-0.5; b₁₂ and b₂₁ are typically 100-5000 J/mol, determined experimentally.
Q2: How do I ensure mole fractions sum to 1?
A: The calculator doesn't enforce this - ensure x₁ + x₂ = 1 for accurate results.
Q3: What temperature units should I use?
A: Temperature must be in Kelvin (K = °C + 273.15).
Q4: Can I use this for multi-component systems?
A: This calculator is for binary systems only. Multi-component NRTL requires additional terms.
Q5: Where can I find NRTL parameters for my system?
A: Check thermodynamic databases like DECHEMA or published literature for your specific components.