29. Calculate the calcium ion concentration in a saturated solution of calcium fluoride.

30. A solution is made 0.10 molar in Mg²⁺, 0.10 molar in NH₃, and 1.0 molar in NH₄Cl. Will Mg(OH)₂ precipitate?

31. In the precipitation of metal sulfides, selective precipitation can be achieved by adjusting the hydrogen ion concentration. At what pH does ZnS begin to precipitate from a 0.077-molar solution of H2S containing 0.08-molar Zn²⁺? (Necessary data are in the tables of K_a and K_sp on Pages 8 and 34.)

32. What is the solubility of AgOH in a buffer at pH 13?

33. In a water solution saturated with H₂S, [H⁺]^₂ [S^2-] = 1.3 x 10^-21 . Calculate the solubility of FeS at pH = 9 and at pH = 2. Can you see how this behavior might be useful in analytical separations?

34. Calculate the solubility of Mg(OH)₂ in aqueous solution at pH = 2 and pH = 12. How is this behavior useful in chemical separations?