Chemistry 18.3 Slide 1 of 27 18.3 Solubility Equilibrium Barium sulfate is ingested by a patient before X-ray images of the digestive tract are taken. Barium sulfate absorbs the Xrays, thereby producing light areas on the developed X-ray film. However, barium salts are usually toxic. You will learn why patients can ingest this poisonous substance without harm. © Copyright Pearson Prentice Hall Slide 2 of 27 18.3 Solubility Equilibrium > The Solubility Product Constant The Solubility Product Constant What is the relationship between the solubility product constant (Ksp) and the solubility of a compound? Slide 3 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Solubility Product Constant The solubility product constant (Ksp), equals the product of the concentrations of the ions, each raised to a power equal to the coefficient of the ion in the dissociation equation. The smaller the numerical value of the solubility product constant, the lower the solubility of the compound. Slide 4 of 27 © Copyright Pearson Prentice Hall Solubility Equilibrium > e.g. Write the Ksp expression for: (i) AgCl (ii) BaSO4 (i) Ionization Equation: AgCl(s) (iii) PbCl2 Ag+(aq) + Cl-(aq) Ksp = [Ag+(aq)] [Cl-(aq) ] (ii) Ionization Equation: BaSO4(s) Ba2+(aq) + SO42-(aq) Ksp = [Ba2+(aq) ] [SO42-(aq)] (iii) Ionization Equation: PbCl2(s) Pb2+(aq) + 2 Cl-(aq) Ksp = [Pb2+(aq) ] [Cl-(aq)]2 Slide 5 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Solubility Product Constant Slide 6 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Solubility Product Constant Slide 7 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Solubility Product Constant Silver chloride is slightly soluble in water. Slide 8 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Solubility Product Constant Scale, formed by the precipitation of slightly soluble salts, builds up around faucets. Slide 9 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.3 Slide 10 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.3 Slide 11 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.3 Slide 12 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.3 Slide 13 of 27 © Copyright Pearson Prentice Hall Practice Problems for Sample Problem 18.3 Problem Solving 18.17 Solve Problem 17 with the help of an interactive guided tutorial. Slide 14 of 27 © Copyright Pearson Prentice Hall Practice Problems More difficult problem : What will be the Pb2+ ion concentration and Clion concentration in a saturated solution of lead (II) chloride? (Ksp = 1.7 x 10-5) Let’s try it on the board… Slide 15 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Common Ion Effect The Common Ion Effect How can you predict whether precipitation will occur when two salt solutions are mixed? Slide 16 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Common Ion Effect If the product of the concentrations of two ions in the mixture is greater than the Ksp of the compound formed from the ions, a precipitate will form. Slide 17 of 27 © Copyright Pearson Prentice Hall Solubility Equilibrium > Sample Problem (taken from p.565): Will a precipitate form when 0.500L of 0.002M Ba(NO3 )2 reacts with 0.500L of 0.008M Na2SO4? [Ksp (BaSO4) = 1.1 x 10-10] Let’s go to the board… Slide 18 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium > The Common Ion Effect A common ion is an ion that is found in both salts in a solution. The lowering of the solubility of an ionic compound as a result of the addition of a common ion is called the common ion effect. Example: adding lead (II) nitrate to an existing saturated solution of lead (II) chromate (see next page). Slide 19 of 27 © Copyright Pearson Prentice Hall 18.3 Solubility Equilibrium A saturated solution of lead(II) chromate is pale yellow. > The Common Ion Effect When a few drops of lead nitrate are added to the solution, more lead(II) chromate Slide precipitates. 20 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.4 Slide 21 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.4 Slide 22 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.4 Slide 23 of 27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 18.4 Slide 24 of 27 © Copyright Pearson Prentice Hall Practice Problems for Sample Problem 18.4 Problem Solving 18.19 Solve Problem 19 with the help of an interactive guided tutorial. Slide 25 of 27 © Copyright Pearson Prentice Hall 18.3 Section Quiz. Assess students’ understanding of the concepts in Section 18.3. Continue to: -or- Launch: Section Quiz Slide 26 of 27 © Copyright Pearson Prentice Hall 18.3 Section Quiz. 1. What is the concentration of a saturated solution of silver sulfide? The Ksp of Ag2S is 8.0 10-51. a. 2.0 10-17M b. 8.9 10-26M c. 8.9 10-25M d. 2.0 1017M Slide 27 of 27 © Copyright Pearson Prentice Hall 18.3 Section Quiz. 2. Adding which of these solutions to a saturated solution of BaSO4 will cause the solubility of BaSO4 to decrease? I. BaCl2(aq) II. Na2SO4 (aq) a. (I) only b. (II) only c. (I) and (II) d. neither solution Slide 28 of 27 © Copyright Pearson Prentice Hall 18.3 Section Quiz. 3. The Ksp of AgBr is 5.0 10-13. When 7.1 10-6 mol/L solutions of NaBr(aq) and AgNO3(aq) are mixed, we would expect a. no precipitate to form. b. a definite precipitation reaction. c. no reaction. d. a saturated solution but no visible precipitation. Slide 29 of 27 © Copyright Pearson Prentice Hall 18.3 Section Quiz. 4. After the common ion effect causes a precipitate to form in a solution, a. the solution will no longer be saturated. b. the solution will again be saturated. c. the solution will be supersaturated. d. there will be no solute left in the solution. Slide 30 of 27 © Copyright Pearson Prentice Hall END OF SHOW