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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
Consider the formation of nitrogen dioxide from nitric oxide and oxygen: 2NO(g) + O2(g) -> 2NO2(g) If 9.0L of NO are reacted with excess O2 at STP, what is the volume in liters of the NO2 produced?
a certain substance has a molar enthalpy of vaporization of 31.6 kj mol. How much of the substance is in a sample that requires 57.0kJ to vaporize?
a student produces 2.73 g of a compound. She calculates the theoretical yield as 3.40 g. What is the percent yield
A flask contains 0.110 mol of liquid bromine, Br2. Determine the number of bromine molecules present in the flask.
An unknown compound X, is thought to have a carboxyl group with a pka of 2.0 and another ionizable group with a pka between 5 and 8. When 75 ml of 0.1 M NaOH was added to 100 ml of a 0.1 m solution of X at pH 2.0, the pH increased to 6.72.
What is the percent dissociation of ascorbic acid if the solution has a pH = 5.50 and a pKa = 4.10?
If you set the freezing point of oleic acid as 0 and the boiling point as 130, what is the freezing point of water on this new scale?
A solution that has a K+ concentration of 5.00ppm is to be prepared from solid KCl. Assuming a solution density of1.000g/mL how many miligrams of KCl must be added to make 1.00L solution?
A 35.00 mL sample of HNO3 solution is neutralized by exactly 42.63 mL of 0.4153 M KOH. What is the molarity of the HNO3 solution?
A mixture at equilibrium at 827 C contains .552 mol CO2, .552 mol H2, .448 mol CO, and .448 mol H20. The balanced equation is shown below: CO2(g) + H2(g) CO(g) + H2O(g) What is the value of Keq?
If two ideal gases are both placed in identical containers with at the same constant Volume and Temp and same number of moles of gas
A 50.0 mL sample of aqueous Ca(OH)2 requires 32.66 mL of a .812 M nitric acid for neutralization. Calculate the concentration (molarity) of the original solution of calcium hydroxide.
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