1 / 18

Outline: 3/12/07

Outline: 3/12/07. Chem. Dept. Seminar Wed @ 4pm 2 more lectures until Exam 2 … Chemistry Advising – Today @ 4pm. Today: More Chapter 18. Polyprotic acid titrations Solubility Product (K sp ). Worksheet #8 practice…. #1a. pH = 2.5

belle
Download Presentation

Outline: 3/12/07

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. Outline: 3/12/07 • Chem. Dept. Seminar Wed @ 4pm • 2 more lectures until Exam 2… • Chemistry Advising – Today @ 4pm Today: • More Chapter 18 Polyprotic acid titrations Solubility Product (Ksp)

  2. Worksheet #8 practice… #1a. pH = 2.5 [H2A] = 0.997 M [HA-] = 0.00316 M [A2-] = 1  10-8 M #1b. pH = 10.5 #2a. pH = 9.74 #2b. pH = 11.1

  3. Quiz # 7 Please put away all books/papers If you don’t have a calculator, just set up the problems fully…

  4. Quiz # 7 Please turn your papers over and pass them to the right…

  5. Quiz #7 : Buffers #1 4.00 = 4.75 + log ([base]/[1.0M]) pH = pKa + log ([base]/[acid]) [base] = 10-0.75 = 0.178 M [base] = 0.178 mol/1.0L = 14.6 g CH3COONa / 1.0L

  6. Quiz #7 : Weak Base #2 0.015-x +x +x Pyr + H2O = pyrH+ + OH- Kb = 10-8.72 = 1.9110-9 1.9110-9 = x2 / 0.015 x = 5.34 10-6 = [OH-] pH = 14 – log( 5.34 10-6) = 8.73

  7. Quiz #7 : Titration #3 HA + OH- A- + H2O (titration) 0.0025 + 0.0005  0 + 0 (init) pH = pKa + log ([base]/[acid]) 0.0020 + 0  0.0005 (equil) pH = 3.74 + log ([0.0005]/[0.0020]) = 3.14

  8. Weak acid: Ka1 = x2/[H2A] Titration of Polyprotic Acids

  9. Buffer: pKa2+log[A]/[HA] Buffer: pKa1+log[HA]/[H2A] Titration of Polyprotic Acids

  10. log((Ka1× Ka2)0.5) See page 785 Titration of Polyprotic Acids

  11. Try example 18 – 12 (page 787) Sulfurous Acid, H2SO3, has two acidic hydrogen atoms, with pKa values of 1.85 and 7.20. Construct a titration curve for the titration of 125 mL of 0.150 M sulfurous acid with 0.800 M NaOH.

  12. Indicators • changes color as the titration passes the stoichiometric point if : pKin≈ pHstoichiometric point

  13. The Solubility-Product Constant, Ksp • Consider • for which • Ksp is the “solubility product”. (BaSO4 is ignored because it is a pure solid so its concentration is constant.)

  14. Solubility Equilibria • The solubility product is another example of equilibrium calculations • Solubility product calcs depend on the common ion effect (LeChâtelier). • They have particular applications with metal ions and pH calculations (environmental applications).

  15. Types of Equilibrium Constants: Lots of different names…. Keq, KH, Ksp, Ka , Kb, Kf , Kc, Kp… All the same idea!

  16. Solubility Equilibria • Insoluble compounds: solubility is less than 0.01 mol of dissolved material per liter of solution, Ksp << 1 • Slightly soluble: 10-5 < Ksp < 10-2 • Soluble: Ksp > 10-2

  17. Solubility Equilibria • The solubility product is another example of equilibrium calculations • Solubility product calcs depend on the common ion effect (LeChâtelier). • They have particular applications with metal ions and pH calculations (environmental applications).

  18. Factors that Affect Solubility • The Common Ion Effect • Solubility is decreased when a common ion is added (Le Châtelier again) • as F- (from NaF, say) is added, the equilibrium shifts left, therefore CaF2(s) is formed (precipitation occurs). • As NaF is added to the system, the solubility of CaF2 decreases.

More Related