1 / 19

______________________________________

Class, Friday, Oct 15, 2004. ______________________________________. Volumetric Chloride Lab is due on Monday, Oct 18 at class time. Homework Assignment 05. __________________________________________. ...is from Chapters 8 & 9. The problems assigned are:

imani-short
Download Presentation

______________________________________

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. Class, Friday, Oct 15, 2004 ______________________________________ Volumetric Chloride Lab is due on Monday, Oct 18 at class time.

  2. Homework Assignment 05 __________________________________________ ...is from Chapters 8 & 9. The problems assigned are: 8-1, 8-4, 8-9, 8-17, 8-22, 8-29 and 9-7, 9-8, 9-10, 9-16, 9-23, 9-24 Wed, Oct 20 Prepare on regularly sized paper, one side only with multiple pages stapled.

  3. Analogs of edta ______________________________________ Additional analogs of edta that are analytically important. All of these also strong 1 : 1 complexes with metal ions.

  4. Kf Formation Constants ______________________________________ The formation reaction for polydentate ligands that form a 1 : 1 complex with metal ions is defined by the reaction M+n + Y-4 < === > MY n-4 and the formation constant Kf = [MY n-4 ] / [M+n] [Y-4] Since the Kf values for most metal-edta complexes are large, it is customary to report them as log10 Kf. The log10 Kf for several metal-edta complexes are given in the next slide.

  5. log Kf for Metal-edta Complexes ______________________________________

  6. Conditional Formation Constants ______________________________________ The actual value of the formation complexes is generally less than that shown in the proceeding slide primarily due to the effects that the pH of the solution have on the complexation reaction. These effects are shown for Ca-edta on the following slide.

  7. log [Ca+2] as a f(pH) ______________________________________

  8. Fig 13-4 ______________________________________ Figure 13-4 pH regions and suggested indicators for EDTA titrations of several metal ions.

  9. EDTA Titration Curves ______________________________________ Figure 13-7 Titration curves for EDTA titrations of Mg+2 and Ca+2 Note that the plot is of pM vs Volume of edta. The shape of the curve is very similar to that of acid base titration curves.

  10. Chemical Equilibrium – Chapter 12 ______________________________________ Although we have already used concepts of equilibrium in previous chapters, we want to take a more detailed look at this important topic.

  11. Chemical Equilibrium ______________________________________ • Chemical equilibrium describes the distribution of the products and reactants in a reaction mixture. • Frequently these relationships are more complicated than first meets the eye. For example, the equilibria (plural) for the solution of slightly soluble lead(II) iodide in water is shown in the next slide.

  12. Chemical Equilibrium ______________________________________ The percent values give the approximate contribution of each species to the whole.

  13. Chemical Equilibrium ______________________________________ Although the model of chemical equilibrium predicts that “inert”, that is, non-reactive salts should not affect the solubility, the actual effect is shown in the next slide, where the addition of KNO3 has caused an increase in the solubility of PbI2. In general the addition of such an inert salt causes an increase the solubility.

  14. Chemical Equilibrium ______________________________________ The solubility of PbI2 as a f(conc of KNO3)

  15. Chemical Equilibrium ______________________________________ Our understanding of the phenomena shown on the previous slide is that the inert salt increases the ionic atmosphere (environment), allowing each cation or anion to be surrounded by species of the opposite charge, but farther separated from the counter ion which caused its original precipitation.

  16. Ionic Environment ______________________________________

  17. Ionic Environment ______________________________________ This effect of the ionic environment within the solution is known as the ionic strength and may be represented as  (your author) or I (other authors).  = I = ½ (c1z12 + c2z22 +…) = ½  cizi2 The sum of terms includes all of the ions in solution. An example of this calculation is shown in Problem 1

  18. Ionic Environment ______________________________________ What is the ionic strength of a solution that is 0.0100 M in KNO3 and 0.0100 M Na2SO4?  = ½  cizi2  = ½ {0.01(+1)2 + 0.01(-1)2 + 0.02(+1)2 + 0.01(-2)2 }  = ½ {0.08} = 0.04M

  19. Activity Coefficients ______________________________________ • The “actual” or “effective” concentration of an ionic species in solution is known as the activity ; your author uses the symbol A(more commonly used is simply a lower case a); • I will use the later symbol, so that his equation 12-2 is written as • aC = [C] C

More Related