Integrated Nature of Chemical Engineering Spring 2005
1. Problem 4.4 from Koretsky’s text: While returning to your dorm/apartment late at night with a hot cup of coffee, the heat overcomes you and, much to your chagrin, you drop the paper cup, spilling its entire contents. As you had just spent your laundry money, this is somewhat upsetting, especially since you still have a good deal of thermo left to study and your last clean pair of pants are now covered with coffee.
You yearn for the old days of polystyrene (Styrofoam) cups, which never got hot. Being an ambitious student (and looking for a distraction), you decide to come up with a process to recycle polystyrene so that environmental concerns will no longer keep the coffee shop from using this very good insulating material.
After several hours, you have come up with what you think is a very reasonable process (you cannot wait to call the patent attorney!) and have just a few final issues to resolve. In the purification process, you believe you have reduced the polystyrene to its monomer, styrene, shown below:
In this case, the reactor would consist of 100 moles of styrene in a volume of 30 L at a pressure of 10 bar. You are concerned that the temperature is beyond the limit for the decomposition of styrene, 289 oC. Since you are studying for a thermo exam, and have just gotten to the van der Waals equation, you want to decide whether this would be a good equation of state to use.
a) What deviations from ideality would you expect at these reaction conditions? List the types of intermolecular forces you think contribute to nonideality in the system. Is the van der Waals equation appropriate? Explain.
b) Your search for experimental values for the van der Waals constants, a and b, is futile; you do, however, find values for the critical constants for styrene:
Pc = 39 bar
Tc = 374 oC
Calculate the temperature of the reactor using the van der Waals equation of state. Will the styrene decompose?
2. Problem 4.30 from Koretsky.
2/4