Lab Schedule. Pages xix and xx (Introduction) of your laboratory manual. Orange Team (Sections AB1, AB3, AB5, BB1, BB3, BB5, BB7): No Change

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1 Lab Schedule Pages xix and xx (Introduction) of your laboratory manual. Orange Team (Sections AB1, AB3, AB5, BB1, BB3, BB5, BB7): No Change No lab 10/27-10/31

2 Lab Schedule Pages xix and xx (Introduction) of your laboratory manual. Blue Team (Sections AB2, AB4, AB6, BB2, BB4, BB6, BB8): No Chromatography lab No lab 10/27-10/31

3 Lecture schedule Pages xxi (Introduction) of your laboratory manual. No lecture 10/22 & 10/27

4 Determination of the solubility of CaSO 4 Solubility Solubility constant Experimental steps Calculation of Ksp

5 Ricin What s in in that white powder? Pb 2+ Anthrax Cd 2+ Saxitoxin Amphetamine As 3+ Psilocybin CN - Hg 2+ Gravimetric analysis Colorimetry Solubility

6 The Concepts A Saturated Solution is in a State of Equilibrium CaSO 4 (s) Ca 2+ + SO 4 2- Every solid, no matter how insoluble, dissolves in solution. Measures of solubility (or insolubility): a. solubility in water: number of g/100 g H 2 O b. solubility product constant: K sp K sp = [Ca 2+ ][SO 4 2- ] The smaller the solubility or K sp value, the less soluble the solid is.

7 An Experiment Using Only One Chemical A Simple System? C = a c CuSO 4 C: conductivity a: constant c: concentration conductivity

8 Determining K sp and solubility Step #1: calibration curve/working curve Make a stock solution of calcium sulfate of a known concentration. Dilute this solution three times to give four solutions of known concentrations Measure the conductivity of each solution. Using Logger Pro, make a graph of concentration vs. conductivity.

9 Determining K sp and solubility Step #2: Determining [Ca 2+ ] and [SO 2-4 ] Measure the conductivity of a saturated solution of calcium sulfate. Using the relationship between concentration and conductivity, find the concentration of the saturated solution.

10 From [Ca 2+ ] and [SO 4 2- ]: Determining K sp and solubility Step #3: Calculations a. K sp = [Ca 2+ ][SO 4 2- ] b. Solubility: Convert molar concentration of dissolved CaSO 4 to grams; Convert volume of water to grams; CaSO 4 in grams/water in grams Determine grams of CaSO 4 in 100 grams of water

11 Step #4 (for your lab report): Compare your experimentally determined K sp and solubility with those in the reference book(s) In the CRC or the Merck, find the K sp value and solubility of calcium sulfate. Compare your experimental values to both constants. Calculate percent errors

12 Step #5: Discuss why the Experimentally determined values are different from those in the reference book(s) K sp is calculated via thermodynamics measuring the free energy change in a reaction at standard state conditions; This does not take into account other effects: e.g., concentrations vs. activity Discuss other potential operational errors in your experiments.

CRC Handbook of Chemistry and Physics Online version: Go to this URL: http://www.hbcpnetbase.com.

13 CRC Handbook of Chemistry and Physics Online version: Go to this URL: Enter the chemical names under Text Search on the upper right corner Several types of information will appear for the chemicals that you searched. Each piece of information has options for viewing (text, table, hits). You can narrow down your search by typing in more search terms Book version: Some information may not be available online In that case, go the Chemistry library and use the book.

Online version: The Merck Index Go to this URL: http://library.dialog.

14 Online version: The Merck Index Go to this URL: Currently not available for uiuc users Book version: Available at the Chemistry library

15 Online version: SciFinder Scholar Go to this URL: Click on under SciFinder Scholar under ARTICLE DATABASES. You can only use SciFinder Scholar at the Chemistry Library and the Chemistry Learning Center. To view the SciFinder Scholar Tutorial, click on SciFinder Scholar Tutorials and Information underneath the heading Tutorials. Book version: No book version

16 Review and Preview Review today s lecture: Read Chapter 5 (pages 47-55) No lecture next week No pre-lab this coming week Next lecture: Characterization of a Weak Acid Read Chapter 7 (Page 69-78) Turn in (last) pre-lab two weeks from today

Lab Schedule. Pages xix and xx (Introduction) of your laboratory manual. Orange Team (Sections AB1, AB3, AB5, BB1, BB3, BB5, BB7): Three (3) week lab

Lab Schedule. Pages xix and xx (Introduction) of your laboratory manual. Orange Team (Sections AB1, AB3, AB5, BB1, BB3, BB5, BB7): Three (3) week lab Lab Schedule Pages xix and xx (Introduction) of your laboratory manual. Orange Team (Sections AB1, AB3, AB5, BB1, BB3, BB5, BB7): Three (3) week lab Lab Schedule Pages xix and xx (Introduction) of your