Chapter 19, Problem 113IE

The following data compare the standard enthalpies and free energies of formation of some crystalline ionic substances and aqueous solutions of the substances:

Substance	ΔHof(kJ/mol)	ΔGof(kJ/mol)
AgNO3(s)	-124.4	-33.4
AgNO3(aq)	-1017	-34.2
MgSO,(s)	-1283.7	-1169.6
MgSO4(aq)	-1374.8	- 1198.4

Write the formation reaction for AgNO₃(s). Based on this reaction, do you expect the entropy of the system to increase or decrease upon the formation of AgNO₃(s)? (b) Use ΔH^o_fand ΔG^o_fof AgNO₃(s) to determine the entropy change upon formation of the substance. Is your answer consistent with your reasoning in part (a)? (c) Is dissolving AgNO₃ in water an exothermic or endothermic process? What about dissolving MgSO₄ in water? (d) For both AgNO₃ and MgSO₄, use the data to calculate the entropy change when the solid is dissolved in water, (e) Discuss the results from part (d) with reference to material presented in this chapter and in the “A Closer Look” box on page 820.