1 / 9

Determination of the Dissociation Constant of a Weak Acid

Determination of the Dissociation Constant of a Weak Acid. Experiment 25 Page 275 Dr. Scott Buzby Ph.D. Objectives. Become more familiar with the operation of a pH meter Quantitatively determine the equilibrium constant of a weak acid (K a ). Acid-Base Equilibria (Strong Acids).

tokala
Download Presentation

Determination of the Dissociation Constant of a Weak Acid

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. Determination of the Dissociation Constant of a Weak Acid Experiment 25 Page 275 Dr. Scott Buzby Ph.D.

  2. Objectives • Become more familiar with the operation of a pH meter • Quantitatively determine the equilibrium constant of a weak acid (Ka)

  3. Acid-Base Equilibria (Strong Acids) • According to Brønsted-Lowry acid-base theory the strength of an acid is related to its ability to donate protons • A strong acid, HCl, will completely dissociate in dilute aqueous solutions • So the [H+] concentration of 0.1M HCl is 0.1M

  4. Acid-Base Equilibria (Weak Acids) • By contrast, weak acids like acetic acid, HC2H3O2 (abbreviated HOAc or HAc) will only partially dissociate • The acid dissociation constant, Ka (equilibrium constant) is used to determine the concentration of H+:

  5. Acid-Base Titration Curve Equivalence Point ½ Equivalence Point

  6. Equivalence Point • At equivalence point the moles of base added equals the moles of acid in unknown sample:

  7. ½ Equivalence Point • ½ equivalence point is the point where ½ the volume of base added to reach equivalence point has been added • At the ½ equivalence point pH of the solution is equal to the pKa of the unknown acid

  8. Experimental Procedure • Skip Part A – Page 279 • Start with Part B – Page 280 • Complete Parts C & D – Page 281

  9. Due Next Week • Report Sheet – Pages 283-285 • Questions – Pages 285-286 • 3 Graphs – Pages 287-289 (or Printouts) • Pre-Lab Experiment 27 – Page 313

More Related