Redlich-Kwong (a - constant)

The Redlich-Kwong Pressure (a - constant) calculator computes the a constant in the Redlich-Kwong equation (below).

INSTRUCTION: Enter the following:

• (T_c)  Critical Temperature of Substance
• (P_c)  Critical pressure of  Substance

Redlich-Kwong (a - constant):  The calculator returns the constant a.  

The Math / Science

In physics and thermodynamics, the Redlich–Kwong equation of state is an empirical, algebraic equation that relates temperature, pressure, and volume of gases. It is generally more accurate than the van der Waals equation and the ideal gas equation at temperatures above the critical temperature.

The Redlich-Kwong equation is:

                `P = (R*T)/(V-b)  - a/(sqrt(T) * V * (V+b))`

where:

• P is the pressure
• R is the Universal Gas Constant
• V is the molar volume
• T is the temperature
• a is the attractive potential correction constant
• b is the volume correction constant

Furthermore:

• a = 0.42748  (R² T_c^2.5)/P_c
• b = 0.8664 (RT_c)/P_c