Chapter 17, Problem 4RQ

The free energy change, ∆G, for a process at constant temperature and pressure is related to ∆S_univ and reflects the spontaneity of the process. How is ∆G related to ∆S_univ? When is a process spontaneous? Nonspontaneous? At equilibrium? ∆G is a composite term composed of ∆H, T, and ∆S. What is the ∆G equation? Give the four possible sign combinations for ∆H and ∆S. What temperatures are required for each sign combination to yield a spontaneous process? If ∆G is positive, what does it say about the reverse process? How does the ∆G = ∆H − T∆S equation reduce when at the melting-point temperature of a solid-to-liquid phase change or at the boiling-point temperature of a liquid-to-gas phase change? What is the sign of ∆G for the solid-to-liquid phase change at temperatures above the freezing point? What is the sign of ∆G for the liquid-to-gas phase change at temperatures below the boiling point?