Critical Pressure Formula:
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Definition: This calculator determines the critical pressure of a real gas using the Wohl equation, which is an empirical thermodynamic equation of state for real gases.
Purpose: It helps in understanding the behavior of real gases at critical conditions, which is important in chemical engineering and thermodynamics.
The calculator uses the Wohl equation formula:
Where:
Explanation: The formula accounts for molecular interactions and finite molecular size through the Wohl parameters.
Details: Critical pressure is essential for designing chemical processes, predicting phase behavior, and understanding gas properties at high pressures.
Tips: Enter all required parameters including temperature, molar volume, Wohl parameters (a, b, c), and reduced pressure. All values must be positive.
Q1: What are typical values for Wohl parameters?
A: Parameters vary by substance. For example, for CO₂: a ≈ 3.59, b ≈ 0.0427, c ≈ 2.32 (units depend on equation form).
Q2: How is reduced pressure determined?
A: Reduced pressure is the ratio of actual pressure to critical pressure (P/Pc). For this calculation, you need experimental or literature values.
Q3: What's the difference between ideal and real gas behavior?
A: Real gases deviate from ideal behavior at high pressures/low temperatures due to molecular interactions and finite molecular volume.
Q4: When is the Wohl equation most accurate?
A: The Wohl equation works well for moderately non-ideal gases but may need modification for highly non-ideal systems.
Q5: How do I find Wohl parameters for a specific gas?
A: Parameters are typically found in thermodynamic databases or determined experimentally from PVT data.