Coordination Chemistry 3 Part 2 Overview Getting Started Techniques Procedure FAQ Full Lab Manual Introduction & Goals Chemistry & Background Key Questions Prelab Problems Safety Procedure In Your Write-up Experiments Index ChemLab Home		Techniques Instruments and equipment used this week include the analytical balance, the Spectronic 20 spectrometer, a Mohr pipet, and volumetric flask. The use of this equipment is described in the Technques section. Procedure Week 3: Preliminary Measurements This week, you will work with a partner, using a single sample of cobalt complex from one person's supply. Start by setting up a distilled water bath in an insulated beaker with a temperature between 35 and 40ƒC. Using the analytical balance, accurately weigh 0.11-0.12 g of cobalt complex. Quantitatively transfer the solid to a 25 mL volumetric flask and add about 20 mL of distilled water. Dissolve the solid and add distilled water until the volume of solution reaches the mark on the flask. Invert and shake the flask to assure quantitative mixing. Use a graduated cylinder or Mohr pipet to measure 10 mL of your cobalt complex solution and place it in a small Erlenmeyer flask. In a second Erlenmeyer flask, place 10 mL of the supplied HNO2/NaNO2 solution. Suspend both flasks in your water bath with copper wire and allow them to reach the temperature of your water bath. Suspend an empty cuvet in the water bath also, so it will be at the correct temperature, when you begin your kinetics run. While waiting for your samples to reach the desired temperature, set the wavelength of your spectrometer to 500 nm and calibrate it using a blank of distilled water. Use a Mohr pipet to transfer 3 mL of your cobalt solution from the volumetric flask to a cuvet and add 3 mL of distilled water. Mix the solution in the cuvet and measure its absorbance, as an initial absorbance value in your analysis. When the solutions in the temperature bath have reached a stable temperature between 35 and 40ƒC, use a Mohr pipet to transfer 3 mL of each solution into the warm, empty cuvet. Cover and invert the cuvet to mix the solutions thoroughly and record the time, since this will be t=0 for the kinetics run. Return the cuvet to the temperature bath and monitor the absorbance of the solution at appropriate intervals of 3 minutes or less, for long enough to determine the structure of the product that is formed and whether a second structure is formed afterwards. This should be a minimum of 45 minutes. Plot absorbance at 500 nm vs. time as you measure it.
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