Chapter 16: Solubility Equilibria Unsaturated solutions Solute  solution NaCl (s)  Na+ (aq) + Cl- (aq) Saturated solutions Point of saturation NaCl (s) ↔ Na+ (aq) + Cl- (aq)

Chapter 17: SOLUBILITY: Ksp Ksp is Solubility-Product Constant Ksp is the solubility product. (BaSO4 is ignored because it is a pure solid so its concentration is constant.)

SOLUBILITY: Ksp Write the Ksp expression for the following: Ca3(PO4)2 (s) ↔ 3Ca2+ (aq) + 2PO43- (aq)

Chapter 16: Ksp Expressions 1. Can use Ksp Expression to calculate maximal solubility. Term “solubility” applies to point of saturation. Weight Solubility is the maximal amount (grams) of solute that can be dissolved in a given volume of solvent. Molar solubility is the maximal amount of moles of solute that can be dissolved to form a liter of saturated solution.

SOLUBILITY: Ksp Expressions (2) CAN USE EXPRESSION TO DETERMINE THE EFFECT OF A COMMON ION ON SOLUBILITY Solubility is decreased when a common ion is added. Ca3(PO4)2 (s) ↔ 3Ca2+ (aq) + 2PO43- (aq) Add Na3PO4 3Na+ (aq) + PO43- (aq) Apply LeChatelier’s Principle

Problem Ksp = [Pb2+] [2Br-]2 The molar solubility of PbBr2 at 25 C is 1.0E-2 moles/liter. Calculate Ksp. PbBr2 (s) ↔Pb2+(aq) + 2Br-(aq) Ksp = [Pb2+] [2Br-]2

Factors That Affect Solubility Common-Ion Effect

Problem Calculate the solubility of CaF2 in grams per liter in (a) pure water; (b) 0.15 M KF solution. Ksp = 3.9E-11 Ksp = [Ca2+] [F-]2

Problem Calcium sulfate is found in plaster. At 25 Celsius Degrees, the value of Ksp for CaSO4 is 2.4E-5. What is the calculated molar solubility of CaSO4 in water?

Solubility: Effect of pH Sr(OH)2 (s)  Sr2+(aq) + 2OH-(aq) Will the addition of H+ have an effect of the solubility of Sr(OH)2 Will the addition of OH- have an effect on the solubility of Sr(OH)2

Solubility: Effect of pH Amphoteric Solutes

Problem Calculate the molar solubility of Mg(OH)2 in a solution that is basic with a pH of 9.50. Ksp for Mg(OH)2 = 7.1E-12

SOLUBILITY: REACTION QUOTIENT (Q) Sr(OH)2 (s)  Sr2+(aq) + 2OH-(aq Q = [Sr2+] [OH-]2 Q = K At point Saturation Q > K Saturated; will precipitate Q < K Unsaturated

Problem Will Ca(OH)2 precipitate if the pH of 0.050 M CaCl2 is adjusted to 8.0 . Ca(OH)2  Ca2+ (aq) + 2OH- (aq) Q = [Ca2+] [OH-]2 Ksp = 6.5E-6

Qualitative Analysis for Metallic Elements Qualitative analysis is designed to detect the presence of metal ions. Quantitative analysis is designed to determine how much metal ion is present.