Which of the following statements is true?

Question

A. Bubble-point pressure calculations are normally easier than bubble-point temperature calculations, since the pure-component vapor pressures are fixed (since the system is at constant temperature).
B. When you flash a liquid by lowering the pressure isothermally, the result will always be a two-phase (liquid and vapor) system.
C. If given the preference between data obtained experimentally or data obtained from a model, it is generally best to use the model data since those do not contain experimental errors.
D. Azeotropes will only form for systems when they exhibit positive deviations from Raoult’s Law.
E. None of the above are true.

Answer 1

A. Correct. The pure-component vapor pressures are only functions of temperature, so when T is fixed, they are fixed. When varying T, the vapor pressures also vary, so one has to solve a non-linear equation to obtain the temperature.
B. Incorrect. It is possible to drop the pressure so little that no flash occurs or drop the pressure so much that ALL the liquid flashes into vapor.
C. Incorrect. Models are regularly parameterized from experimental data, and so will incorporate any errors from that experimental data. Additionally, the model may not describe the components accurately.
D. Incorrect. Both positive and negative deviation exhibiting systems may be azeotropic. Figure 10-5 and Figure 10-6 show a positive deviating azeotropic system and a negative deviating azeotropic system, respectively.
E. Incorrect. One of the statements is true.