1. What is Residual Gibbs Free Energy?

Definition: Residual Gibbs Free Energy is the difference between the Gibbs energy of a real system and that of an ideal system at the same temperature and pressure.

Purpose: It quantifies the deviation from ideal behavior in thermodynamic systems and is crucial for understanding real gas behavior and phase equilibria.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( G^R \) — Residual Gibbs Free Energy (Joules)
• \( [R] \) — Universal gas constant (8.314 J/mol·K)
• \( T \) — Temperature (Kelvin)
• \( f \) — Fugacity (Pascal)
• \( P \) — Pressure (Pascal)

Explanation: The natural logarithm of the fugacity-pressure ratio is multiplied by temperature and the gas constant to calculate the residual Gibbs energy.

3. Importance of Residual Gibbs Energy Calculation

Details: This calculation is essential for chemical engineering thermodynamics, particularly in process design, phase equilibrium calculations, and non-ideal system analysis.

4. Using the Calculator

Tips: Enter temperature in Kelvin, fugacity and pressure in Pascals. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is fugacity?
A: Fugacity is a thermodynamic property that represents the "effective pressure" of a real gas, accounting for non-ideal behavior.

Q2: When is residual Gibbs energy positive vs negative?
A: Positive when f > P (repulsive interactions dominate), negative when f < P (attractive interactions dominate).

Q3: What units should I use?
A: Temperature in Kelvin, fugacity and pressure in Pascals. The result is in Joules.

Q4: Can I use this for liquid phases?
A: Yes, the concept applies to any phase, but ensure you have accurate fugacity data for liquids.

Q5: How does temperature affect the result?
A: Higher temperatures amplify the effect of non-ideality (larger absolute GR values for same f/P ratio).