16.1 Solubility Equilibria and the Solubility ProductSolubility Equilibria• Solubility product (Ksp) – Equilibrium constant; has only one value for a given solid at a given temperature.• Solubility – an Equilibrium position.16.2 Precipitation and Qualitative AnalysisPrecipitation (Mixing Two Solutions of Ions)Ion product:• Q > Ksp; precipitation occurs and will continue until the concentrations are reduced to the point that they satisfy Ksp.• Q < Ksp; no precipitation occurs.A solution is prepared by adding 750.0 mL of 4.00x10-3 M Ce(NO3)3 to 300.0 mL of 2.00x10-2 M KIO3. Will Ce(IO3)3 (Ksp=1.9x10-10) precipitate from this solution?Selective Precipitation (Mixtures of Metal Ions) Qualitative Analysis• Use a reagent whose anion forms a precipitate with only one or a few of the metal ions in the mixture.• Example: Solution contains Ba2+ and Ag+ ions. Adding NaCl will form a precipitate with Ag+ (AgCl), while still leaving Ba2+ in solution.A solution contains 1.0x10-4 M Cu+ and 2.0x10-3 M Pb2+. If a source of I- is added gradually to this solution, will PbI2 (Ksp= 1.4x10-8) or CuI (Ksp= 5.3x10-12) precipitate first? Specify the concentration of I- necessary to begin precipitation of each salt.Separation of Cu2+ and Hg2+ from Ni2+ and Mn2+ using H2S• Metal sulfide salts differ dramatically in their solubility• At a low pH, [S2–] is relatively low and only the very insoluble HgS and CuS precipitate.• When OH– is added to lower [H+], the value of [S2–] increases, and MnS and NiS precipitate.Qualitative Analysis: Separating the Common Cations by Selective PrecipitationGroup I: Insoluble chloridesGroup II: Sulfide insoluble in acidic solution.Group III: Sulfide insoluble in basic solution.Group IV: Insoluble carbonateGroup V: Alkali metal and NH4+16.3 Equilibria Involving Complex Ions