广西招聘及附件.docVIP

Question 6-1 Why should we develop Maxwell equations and their derivatives? Answer: Because the Maxwell equations connect properties such as the enthalpy and entropy to commonly measured quantities such as pressure, volume, temperature and heat capacity. So we can calculate thermodynamic properties from the available experimental date by these correlations. 6-2 What is the equation of the chemical potential component i and where it can play a vital role? Answer The quantityμi is called the chemical potential component i and it can play a vital role in phase and chemical equilibria 6-3 Why the pair quantities T and P are often chosen to express other thermodynamic properties? Answer:The pair usually chosen is T and P, because these quantities are readily measured. If we consider the enthalpy H and entropy S to be functions of these variables, then what we wish to know is how H and S vary with T at constant P and how they vary with P at constant T. This information is provided by the derivatives (H/T)P, (S/T)P, (H/P)T , and(S/P)T. 6-4. What role does the Gibbs free energy play in phase and chemical equilibria? Answer: The Gibbs free energy plays a central role in phase and chemical equilibria. The molar or specific Gibbs free energy dose not change during a phase change such as melting, vaporization, or sublimation. If a differential amount of liquid is caused to evaporate at constant temperature and pressure, Eq. (6-6) shows that dGt=0 for the process. This requires the molar (or specific) free energy of the vapor to be identical with that for the liquid. More generally, for two coexisting phase α and β of a pure substance, Gα=Gβ where Gα and Gβ are the molar (or specific) Gibbs free energies of the two phases. 6-5 What is the concept of residual properties and why should we develop this concept? Answer :Residual properties relate the real state of a fluid to its ideal-gas state at the same fixed temperature and pressure. They