Critical Pressure of Real Gas using Wohl Equation given Reduced and Actual Parameters Calculator

Critical Pressure Formula:

\[ P_c = \frac{\frac{[R]T_r}{V'_m - b} - \frac{a}{T_r V'_m (V'_m - b)} + \frac{c}{(T_r^2)(V'_m^3)}}}{P_r} \]

Temperature of Real Gas:

Molar Volume of Real Gas:

m³

Wohl Parameter b:

Wohl Parameter a:

Wohl Parameter c:

Reduced Pressure:

Critical Pressure (Pa):

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1. What is Critical Pressure of Real Gas using Wohl Equation?

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.

2. How Does the Calculator Work?

The calculator uses the Wohl equation formula:

\[ P_c = \frac{\frac{[R]T_r}{V'_m - b} - \frac{a}{T_r V'_m (V'_m - b)} + \frac{c}{(T_r^2)(V'_m^3)}}{P_r} \]

Where:

\( P_c \) — Critical Pressure (Pa)
\( T_r \) — Temperature of real gas (K)
\( V'_m \) — Molar volume of real gas (m³)
\( a, b, c \) — Wohl parameters (empirical constants)
\( P_r \) — Reduced pressure (dimensionless)
\( [R] \) — Universal gas constant (8.314 J/mol·K)

Explanation: The formula accounts for molecular interactions and finite molecular size through the Wohl parameters.

3. Importance of Critical Pressure Calculation

Details: Critical pressure is essential for designing chemical processes, predicting phase behavior, and understanding gas properties at high pressures.

4. Using the Calculator

Tips: Enter all required parameters including temperature, molar volume, Wohl parameters (a, b, c), and reduced pressure. All values must be positive.

5. Frequently Asked Questions (FAQ)

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.