Redlich-Kwong Equation Formulas |
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| \( p \;=\; \dfrac{ R \cdot T_a }{ V - b } - \dfrac{ a }{ \sqrt{T_a} \cdot V \cdot (V + b ) } \) | ||
| Symbol | English | Metric |
| \( p \) = Fluid Pressure | - | \(m^3\;/\;mol\) |
| \( R \) = Universal Gas Constant | - | \(J\;/\;kmol-K\) |
| \( T_a \) = Absolute Temperature | - | \(^\circ K\) |
| \( V \) = Fluid Molar Volume | - | \(m^3 \;/\;mol\) |
| \( b \) = Volume (Molecular Size) | - | \(m^3 \;/\;mol\) |
| \( a \) = Attractive Force | - | \(Pa \cdot m^6 \cdot K^{0.5} \;/\;mol^2\) |
Redlich–Kwong equation of state is a thermodynamic model used to describe the pressure–volume–temperature (PVT) behavior of real gases, improving on the ideal gas law by accounting for intermolecular attractions and the finite size of gas molecules. It modifies the van der Waals approach by making the attractive force term temperature dependent, which significantly increases accuracy at moderate to high temperatures and pressures.
The equation relates pressure, molar volume, and temperature through substance-specific constants derived from critical properties, allowing it to better predict gas behavior near non-ideal conditions. Although it is less accurate near the critical point and for strongly polar substances, the Redlich–Kwong equation remains important in chemical and mechanical engineering as a foundation for more advanced cubic equations of state, such as the Soave–Redlich–Kwong and Peng–Robinson models.
Redlich-Kwong Equation Formula
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\( b \;=\; 0.08664 \cdot \dfrac{ R \cdot T_c }{ P_c } \) \( a \;=\; 0.42748 \cdot \dfrac{ R^2 \cdot T_c^{2.5} }{ P_c } \) |
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| Symbol | English | Metric |
| \( b \) = Volume (Molecular Size) | - | \(m^3\;/\;mol\) |
| \( a \) = Attractive Force | \(Pa \cdot m^6 \cdot K^{0.5} \;/\;mol^2\) | |
| \( R \) = Universal Gas Constant | - | \(J\;/\;kmol-K\) |
| \( T_c \) = Critical Temperature | - | \(^\circ K\) |
| \( P_c \) = critical Pressure | - | \(Pa\) |
