Chapter 14

Substance A is a nonpolar liquid and has only dispersion forces among its constituent particles. Substance \(\mathrm{B}\) is also a nonpolar liquid and has about the same magnitude of dispersion forces among its constituent particles as substance A. When substance A and substance \(\mathrm{B}\) are combined, they spontaneously \(\mathrm{mix}\). a. Why do the two substances mix? b. Predict the sign and magnitude of \(\Delta H_{\text {soln. }}\) c. Determine the signs and relative magnitudes of \(\Delta H_{\text {solute }}\) \(\Delta H_{\text {solvent }},\) and \(\Delta H_{\text {mix }}\)

A power plant built on a river uses river water as a coolant. The water is warmed as it is used in heat exchangers within the plant. Should the warm water be immediately cycled back into the river? Why or why not?

If each substance listed here costs the same amount per kilogram, which would be most cost-effective as a way to lower the freezing point of water? (Assume complete dissociation for all ionic compounds.) Explain. a. \(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) b. \(\mathrm{NaCl}\) c. KCl d. \(\mathrm{MgCl}_{2}\) e. \(\mathrm{SrCl}_{2}\)

Have each group member make a flashcard with one of the following on the front: \(\Delta H_{\text {soln }}, \Delta H_{\text {lattice, }} \Delta H_{\text {solvent, }} \Delta H_{\text {mix }},\) and \(\Delta H_{\text {hydration. }}\) On the back of the card, each group member should describe (in words) the \(\Delta H\) process his or her card lists and how that \(\Delta H\) relates to other \(\Delta H\) values mathematically. Each member presents his or her \(\Delta H\) to the group. After everyone has presented, members should trade cards and quiz each other.