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

Wohl Equation Formula:

\[ P = \frac{RT_rT_c}{(V_rV_c - b)} - \frac{a}{T_rT_cV_rV_c(V_rV_c - b)} + \frac{c}{(T_rT_c)^2(V_rV_c)^3} \]

Reduced Temperature:

Critical Temperature (K):

Reduced Molar Volume:

Critical Molar Volume (m³/mol):

Wohl Parameter b:

Wohl Parameter a:

Wohl Parameter c:

Pressure of Gas (Pa):

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1. What is Wohl Equation for Real Gas Pressure?

Definition: The Wohl equation is a thermodynamic equation of state used to calculate the pressure of real gases, accounting for molecular size and intermolecular forces.

Purpose: It provides more accurate pressure calculations than the ideal gas law for real gases under various conditions.

2. How Does the Calculator Work?

The calculator uses the Wohl equation:

\[ P = \frac{RT_rT_c}{(V_rV_c - b)} - \frac{a}{T_rT_cV_rV_c(V_rV_c - b)} + \frac{c}{(T_rT_c)^2(V_rV_c)^3} \]

Where:

\( P \) — Pressure of gas (Pascal)
\( R \) — Universal gas constant (8.314 J/mol·K)
\( T_r \) — Reduced temperature (dimensionless)
\( T_c \) — Critical temperature (Kelvin)
\( V_r \) — Reduced molar volume (dimensionless)
\( V_c \) — Critical molar volume (m³/mol)
\( a, b, c \) — Wohl parameters specific to each gas

3. Importance of Wohl Equation

Details: The Wohl equation provides more accurate results than ideal gas law for real gases, especially near critical points where intermolecular forces become significant.

4. Using the Calculator

Tips: Enter all required parameters including reduced temperature, critical temperature, reduced molar volume, critical molar volume, and the three Wohl parameters (a, b, c).

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for Wohl parameters?
A: Wohl parameters vary by gas. For example, for CO₂: a ≈ 3.59, b ≈ 0.0427, c ≈ 0.00263 (units depend on the equation form).

Q2: How do I get reduced temperature and volume?
A: Reduced temperature = T/Tc, Reduced volume = V/Vc, where T and V are actual conditions.

Q3: When is the Wohl equation most accurate?
A: For moderate pressures, not too close to the critical point or at extremely high pressures.

Q4: How does this compare to van der Waals equation?
A: Wohl equation includes an additional term (c parameter) for better accuracy with polar gases.

Q5: What are common applications?
A: Chemical engineering calculations, gas processing, and thermodynamic analysis of real gases.