Experiment 9

1
Experiment 9

• Preparation and Analysis of a Coordination
  Compound

2
Goals

• Synthesize chloropentaaminocobalt chloride
  Co(NH3)5ClCl2
• 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)63

• 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 yield100

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 _______________________________