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Experiment 9

Experiment 9. Preparation and Analysis of a Coordination Compound. Goals. Synthesize chloropentaaminocobalt chloride [Co(NH 3 ) 5 Cl]Cl 2 Determine __________ of product

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Experiment 9

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  1. Experiment 9 Preparation and Analysis of a Coordination Compound

  2. Goals • Synthesize chloropentaaminocobalt chloride [Co(NH3)5Cl]Cl2 • Determine __________ of product • Analyze product by column chromatography and Atomic Absorption Spectroscopy to determine its __________ and, therefore, _______________________ ______________________________________

  3. Hazards • Cobalt compounds (including starting material and all products) • Hydrogen Peroxide • Ammonium hydroxide • Ammonium chloride • Hydrochloric Acid • Methanol

  4. What is a Coordination Compound? • “metal atom or ion associated with a group of neutral molecules or anions”* • In water, _____________ will surround an ion • Sometimes, when the ions are crystallized they retain one or more H2O molecules as a ligand • The H2O molecules are considered to be _________________________________________ • Ligands form _______________ (they donate the electrons) with ________________ • Coordination complexes contain the coordination compound plus additional ions to balance charge [coord Cmpd] ions *Kotz, J. Treichel, P., Chemistry and Chemical Reactivity, 4th Ed., 1999.

  5. Co(NH3)6+3 Octahedrally surrounded to give compact sphere *from http://genchem.rutgers.edu/CoAm.html

  6. The Planned Mechanism +2 +1 +OH-+6NH3 + NH4+ + 5H2O NH4Cl/NH4OH +1 +2 +½H2O2  Oxidizes Co from +2 to +3

  7. Planned Mechanism continued +3 +2 + H+  From HCl +2 +3 + Cl- 

  8. The Analysis-Next Week • How much cobalt should be in the product? • What if you determine that it is not the calculated value? • What should the final charge be for the product? • Can you get something else? • What does the charge that you get depend on?

  9. Week 1 Results • Whenever you make something, what do you usually want to know? • %Yield – will be calculated next week • What does it tell? • %yield = Actual yield/theoretical yield*100%

  10. Theoretical Yield???? • Weigh amount of limiting substance • Change grams to moles • Determine how many moles of product this could make • Take into account stoichiometry • For today: 1mol reagent: 1mol product • Change to grams of product

  11. Critical Measurements

  12. Introduction • Steps in synthesis • What is the __________________________ • What _______________________________ • Why _________________________________ • Why ________________________________ • Co concentration Analysis by AAS • What is _____________ • Why _________________ • How _____________________ • What major principle governs this method • _____________________________________ • What the ___________________________ • Charge Analysis by IEC • What is ______________________ • How does it work • What is coming off of the column, where did it come from, what do you do with it • How ___________________________________________ • Why ________________________________________ • The _______________________________

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