Experiment 9 Preparation and Analysis of a Coordination Compound

Goals Synthesize chloropentaaminocobalt chloride [Co(NH 3 ) 5 Cl]Cl 2 Determine __________ of product Analyze product by column chromatography and Atomic Absorption Spectroscopy to determine its __________ and, therefore, _______________________ ______________________________________

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

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 H 2 O molecules as a ligand The H 2 O 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, 4 th Ed., 1999.

Co(NH 3 ) 6 +3 Octahedrally surrounded to give compact sphere *from

The Planned Mechanism +OH - +6NH 3  NH 4 Cl/NH 4 OH + NH H 2 O ½H 2 O 2  Oxidizes Co from +2 to

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

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?

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%

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

Critical Measurements

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 _______________________________