Critical Pressure Formula:
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Definition: Critical pressure is the minimum pressure required to liquify a substance at its critical temperature.
Purpose: This calculator determines the critical pressure using the Clausius equation of state for real gases.
The calculator uses the Clausius equation:
Where:
Details: Critical pressure is essential for understanding phase behavior, designing chemical processes, and predicting gas liquefaction conditions.
Tips: Enter all required parameters with positive values. Default values are provided for Clausius parameters a, b, c and reduced pressure.
Q1: What are typical values for Clausius parameters?
A: Parameters vary by gas. For example, for CO₂: a ≈ 0.3653 Pa·m⁶/mol², b ≈ 4.28×10⁻⁵ m³/mol, c ≈ 0.0428×10⁻⁵ m³/mol.
Q2: How do I find reduced pressure?
A: Reduced pressure is the ratio of actual pressure to critical pressure (P/Pc).
Q3: What units should I use?
A: Use Kelvin for temperature, m³/mol for molar volume, and dimensionless for reduced pressure.
Q4: Why does the Clausius equation include parameters a, b, c?
A: These empirical parameters account for intermolecular forces (a), molecular volume (b), and other non-ideal gas effects (c).
Q5: What's the range of validity for this equation?
A: The Clausius equation works best at moderate pressures, not too close to the critical point.