Critical Pressure of Real Gas using Reduced Redlich Kwong Equation Calculator

Critical Pressure Formula:

\[ P_c = \frac{P}{\left(\frac{3T_r}{V_{m,r}-0.26}\right)-\left(\frac{1}{0.26\sqrt{T_g}V_{m,r}(V_{m,r}+0.26)}\right)} \]

Pressure (P):

Reduced Temperature (T_r):

Reduced Molar Volume (V_m,r):

Temperature of Gas (T_g):

Critical Pressure (P_c): Pa

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1. What is Critical Pressure of Real Gas?

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 Reduced Redlich Kwong Equation, which is important in thermodynamics and chemical engineering.

2. How Does the Calculator Work?

The calculator uses the Reduced Redlich Kwong Equation:

\[ P_c = \frac{P}{\left(\frac{3T_r}{V_{m,r}-0.26}\right)-\left(\frac{1}{0.26\sqrt{T_g}V_{m,r}(V_{m,r}+0.26)}\right)} \]

Where:

\( P_c \) — Critical Pressure (Pascal)
\( P \) — Applied Pressure (Pascal)
\( T_r \) — Reduced Temperature (dimensionless)
\( V_{m,r} \) — Reduced Molar Volume (dimensionless)
\( T_g \) — Temperature of Gas (Kelvin)

Explanation: The equation accounts for real gas behavior by incorporating reduced properties and temperature corrections.

3. Importance of Critical Pressure Calculation

Details: Knowing the critical pressure is essential for designing chemical processes, storage systems, and understanding phase behavior of substances.

4. Using the Calculator

Tips: Enter the pressure in Pascals, reduced temperature (dimensionless), reduced molar volume (must be > 0.26), and gas temperature in Kelvin.

5. Frequently Asked Questions (FAQ)

Q1: What is reduced temperature?
A: Reduced temperature is the ratio of the actual temperature to the critical temperature of the substance (T/T_c).

Q2: What is reduced molar volume?
A: Reduced molar volume is the actual molar volume divided by the critical molar volume (V_m/V_c).

Q3: Why must reduced molar volume be greater than 0.26?
A: The equation becomes undefined at V_m,r ≤ 0.26 due to the denominator term (V_m,r - 0.26).

Q4: What are typical values for reduced temperature?
A: Values typically range from 0.5 to 2.0, with 1.0 representing the critical point.

Q5: How accurate is the Reduced Redlich Kwong Equation?
A: It provides reasonable estimates for many real gases, especially non-polar ones, but may need modification for polar substances.