1 / 17

Chapter 18: Solubility and Complex-Ion Equilibria

Petrucci • Harwood • Herring • Madura. GENERAL. Ninth Edition. CHEMISTRY. Principles and Modern Applications. Chapter 18: Solubility and Complex-Ion Equilibria. Juana Mendenhall, Ph.D. Assistant Professor Ch 18 Lecture 1 Feb 26, 2010. Objectives.

olympia
Download Presentation

Chapter 18: Solubility and Complex-Ion Equilibria

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Petrucci • Harwood • Herring • Madura GENERAL Ninth Edition CHEMISTRY Principles and Modern Applications Chapter 18: Solubility and Complex-Ion Equilibria Juana Mendenhall, Ph.D. Assistant Professor Ch 18 Lecture 1 Feb 26, 2010 General Chemistry: Chapter 18

  2. Objectives The Solubility Product Constant, Ksp Write the solubility product expression Ksp for a slightly soluble ionic compound The Relationship Between Solubility and Ksp Calculate the effect of common ions on the aqueous solubilities of sparingly soluble salts The Common-Ion Effect in Solubility Equilibria Determine if a salt will precipitate from solution based on the concentration of its ions General Chemistry: Chapter 18

  3. The Solubility Product Constant, Ksp • The equilibrium constant for the equilibrium established between a solid solute and its ions in a saturated solution. CaSO4(s) Ca2+(aq) + SO42-(aq) Ksp = [Ca2+][SO42-] = 9.110-6 at 25°C General Chemistry: Chapter 18

  4. Types of Solubility Equilibria General Chemistry: Chapter 18

  5. The Relationship Between Solubility and Ksp • Molar solubility. • The molarity in a saturated aqueous solution. • Related to Ksp g BaSO4/100 mL → mol BaSO4/L → [Ba2+] and [SO42-] → Ksp = 1.110-10 General Chemistry: Chapter 18

  6. General Chemistry: Chapter 18

  7. The Common-Ion Effect in Solubility Equilibria The ion product (Qsp) is related to the solubility product (Ksp) by Qsp < Ksp, more solute can dissolve Qsp > Ksp, precipitate forms If Qsp = Ksp, the solution is saturated General Chemistry: Chapter 18

  8. The Common-Ion Effect and Le Châtelier’s Principle General Chemistry: Chapter 18

  9. 18-4 Limitations of the Ksp Concept • Ksp is usually limited to slightly soluble solutes. • For more soluble solutes we must use ion activities • Activities (effective concentrations) become smaller than the measured concentrations. • The Salt Effect (or diverse ion effect). • Ionic interactions are important even when an ion is not apparently participating in the equilibrium. • Uncommon ions tend to increase solubility. General Chemistry: Chapter 18

  10. Effects on the Solubility of Ag2CrO4 General Chemistry: Chapter 18

  11. Ion Pairs General Chemistry: Chapter 18

  12. Incomplete Dissociation • Assumption that all ions in solution are completely dissociated is not valid. • Ion Pair formation occurs. • Some solute “molecules” are present in solution. • Increasingly likely as charges on ions increase. Ksp (CaSO4) = 2.310-4 by considering solubility in g/100 mL Table 19: Ksp = 9.110-6 Activities take into account ion pair formation and must be used. General Chemistry: Chapter 18

  13. Simultaneous Equilibria • Other equilibria are usually present in a solution. • Kw for example. • These must be taken into account if they affect the equilibrium in question. General Chemistry: Chapter 18

  14. 18-5 Criteria for Precipitation and Its Completeness AgI(s) Ag+(aq) + I-(aq) Ksp = [Ag+][Cl-] = 8.510-17 Mix AgNO3(aq) and KI(aq) to obtain a solution that is 0.010 M in Ag+ and 0.015 M in I-. Saturated, supersaturated or unsaturated? Q = [Ag+][Cl-] = (0.010)(0.015) = 1.10-4 > Ksp General Chemistry: Chapter 18

  15. The Ion Product Q is generally called the ion product. Q > Ksp Precipitation should occur. Q = Ksp The solution is just saturated. Q < Ksp Precipitation cannot occur. General Chemistry: Chapter 18

  16. EXAMPLE 18-5 0.05 mL 1 L 0.20 mol KI 1 mol I- nI- = 3 drops 1 drop 1 L 1 mol KI 1000 mL Applying the Criteria for Precipitation of a Slightly Soluble Solute. Three drops of 0.20 M KI are added to 100.0 mL of 0.010 M Pb(NO3)2. Will a precipitate of lead iodide form? (1 drop  0.05 mL) PbI2(s) → Pb2+(aq) + 2 I-(aq) Ksp= 7.110-9 Determine the amount of I- in the solution: = 310-5 mol I- General Chemistry: Chapter 18

  17. EXAMPLE 18-5 310-5 mol I- [I-] = = 310-4 M I- 0.1000 L Determine the concentration of I- in the solution: Apply the Precipitation Criteria: Q = [Pb2+][I-]2 = (0.010)(310-4)2 = 910-10 < Ksp= 7.110-9 General Chemistry: Chapter 18

More Related