For an industrial process, it is necessary to
introduce 1400 mols of 1,3,5-trihydroxybenzene at a temperature of 560
K and pressure of 150 kPa in a steel cylinder. Calculate the volume of
the cylinder using the
van der Waals equation, if the a
and b constants are known.
The van der Waals formula is a third degree equation for the volume: Higher degree equations are handled by Mathcad with the root function. The syntax is:
Since an iterative algorithm is used for the calculation, an initial guess value is necessary. It must be borne in mind that for a third degree equation there are three solutions and which root is found depends on the initialization value. Of the three roots, only one will have physical meaning; in other words a negative or a complex value for the volume, although mathematically correct, has no physical meaning.