Chapter 17, Problem 5RQ

What is the third law of thermodynamics? What are standard entropy values, S°_,  and how are these S° values (listed in Appendix 4) used to calculate ∆S° for a reaction? How would you use Hess’s law to calculate ∆S° for a reaction? What does the superscript ° indicate?

Predicting the sign of ∆S° for a reaction is an important skill to master. For a gas-phase reaction, what do you concentrate on to predict the sign of ∆S°? For a phase change, what do you concentrate on to predict the sign of ∆S°? That is, how are $S_{\text{solid}}^{\circ }$, $S_{\text{liquid}}^{\circ }$, and $S_{\text{gas}}^{\circ }$ related to one another? When a solute dissolves in water, what is usually the sign of ∆S° for this process?