JavaScript Programs To Calculate Thermodynamic Properties Using Cubic Equations of State

Cubic equations of state are widely used by chemists and chemical engineers to predict the thermodynamic properties of both pure substances and mixtures. In particular, these equations enable predictions concerning the temperature and pressure at which vapor–liquid equilibrium occurs. These two educational JavaScript programs perform calculations using cubic equations of state and, equally importantly, explain how the calculations are performed.

The first program gives students the choice of five different cubic equations of state and performs calculations for pure substances. It calculates compressibility factor, molar volume, fugacity coefficient and enthalpy, and entropy departure functions.

The second program predicts vapor–liquid equilibrium for binary mixtures using a choice of three modern equations of state and the van der Waals mixing rules. The program calculates bubble point pressures and temperatures, dew point pressures and temperatures, and can do isothermal vapor–liquid flash calculations.

There are several advantages to using JavaScript and a Web interface for these programs. The programs are easily accessible at any time from computers using common Web browsers, and they utilize quick links to theory that the student can access online. Links include information on the equation of state selected, on the theory of vapor–liquid equilibrium (e.g., the difference between a bubble point and a dew point), and on the method of calculation. Another advantage of these programs is that virtually all students are familiar with using forms on Web pages, so they find the program’s use straightforward. The Web interface makes it is easy for students to vary a parameter and observe its influence on the answer, or to repeat a calculation using a different equation of state.