Berthelot Equation Formula:
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Definition: The Berthelot equation is a thermodynamic equation of state for real gases that modifies the ideal gas law to account for molecular size and intermolecular forces.
Purpose: It provides a more accurate calculation of gas pressure under non-ideal conditions, especially at moderate pressures and temperatures.
The calculator uses the Berthelot equation:
Where:
Explanation: The first term accounts for molecular volume exclusion, while the second term accounts for intermolecular attractive forces.
Details: This equation provides better pressure estimates than the ideal gas law when dealing with real gases, especially in chemical engineering and physical chemistry applications.
Tips: Enter the temperature in Kelvin, molar volume in m³/mol, and Berthelot parameters a and b. All values must be positive (except parameters which can be zero).
Q1: What are typical values for Berthelot parameters?
A: Parameters vary by gas. For example, for nitrogen: a ≈ 0.136 Pa·m⁶/mol², b ≈ 3.86×10⁻⁵ m³/mol.
Q2: When is the Berthelot equation most accurate?
A: It works best at moderate pressures (not too high, not too low) and temperatures above the critical temperature.
Q3: How does this differ from van der Waals equation?
A: The Berthelot equation uses temperature-dependent attractive forces (a/T term) while van der Waals uses constant 'a'.
Q4: Can I use this for liquids?
A: No, the Berthelot equation is only valid for gases. Different equations are needed for liquids.
Q5: What units should I use?
A: Use Kelvin for temperature, m³/mol for molar volume, and SI-compatible units for parameters to get pressure in Pascals.