1. In Week 1 of the lab, you determined the percent Co by converting your product into a blue-violet colored Co complex and measuring the absorbance in the Spec 20 instrument. What is the formula of this blue-violet complex?

2. In Week 1 of this lab, you synthesized a cobalt(III) coordination complex containing ethylenediammine as a ligand. You then performed an analysis for percent cobalt using spectrophotometry. Suppose that you dissolved 0.152 g of your green cobalt complex in water, added NaOH to remove all the ligands, and cooked the compound to dryness to make Co2O3. Redissolving this solid in HCl yielded the blue-colored CoCl42- ion. This solution was added to a 250.0-mL volumetric flask, which was filled to the mark with distilled water. Then, 10.00 mL of this solution was pipetted into a 100.0-mL volumetric flask and ammonium thiocyanate was added to make the blue-purple colored Co(SCN)42- ion. The absorbance of Co(SCN)42- was determined by spectrophotometry to be 0.419 and the molar absorptivity of the complex was 1790 M-1cm-1 using a 1.10-cm cuvette. Calculate the percent cobalt in the complex.

3. Given the data in Problem #42, what is the identity of the unknown Co compound?

4. What is the product formed when blue [CoCl4]2- is diluted in water to make a pink solution?

5. Given the two data points below for the kinetics of aquation of the above product, calculate the activation barrier (Ea) for the aquation reaction in units of kJ/mol.

k (s-1) T ( °C)

3.27 x 10-4 38.0

2.20 x 10-3 54.2