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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.
A screenshot of JavaScript Programs To Calculate Thermodynamic
Properties Using Cubic Equations of State
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