A.P. Chemistry
Chapter 13: Properties of Solutions Problem Set
1. A textbook on chemical thermodynamics states, “The heat of solution represents the difference
between the lattice energy of the crystalline solid and the solvation energy of the gaseous ions.”
a. Draw a simple energy diagram of to illustrate this statement
b. A salt such as NaBr is insoluble in most polar nonaqueous solvents such as acetonitrile
(CH3CN) or nitromethane (CH3NO2), but salts of large cations, such as
tetramethylammonium bromide [(CH3)4NBr], are generally more soluble. Use the
thermochemical cycle you drew in part (a) and the factors that determine the lattice
energy to explain this fact.
2. The solubility of Cr(NO3)3 . 9 H2O in water is 208 g per 100 g of water at 150C. A solution of
Cr(NO3)3 . 9 H2O in water at 350C is formed by dissolving 324 g in 100 g water. When this solution
is slowly cooled to 150C, no precipitate forms.
a. What term describes this solution?
b. What action might you take to initiate crystallization? Use molecular-level processes to
explain how your suggested procedure works.
3. Indicate the type of solute-solvent interaction (Section 11.2) that should be most important in
each of the following solutions:
a. CCl4 in benzene (C6H6)
b. Methanol (CH3OH) in water
c. KBr in water
d. HCl in acetonitrile (CH3CN)