Coordination Chemistry 4 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		Preparing for a Kinetics Run Begin by making up a solution of your cobalt complex. Measure the mass of the solid with an analytical balance and make up the solution in a volumetric flask. Setting up reaction to determine A at infinite time Prepare a reaction mixture by pipetting 5 mL of each reactant into an Erlenmeyer flask. You can review the use of a pipet on the Pipet page. Cork your reaction flask and label it. Suspend it in a 70° water bath, supplied by your TA, along with the other flasks of your lab group. Measurement to determine the initial absorbance Pipet 3 mL of your cobalt complex solution and 3 mL of water into a cuvet. Measure the absorbance of your diluted solution at 415 nm and 450 nm. These absorbance values should be equal to the inital absorbance of your reaction mixture, before the ligand substitution reaction begins. Room Temperature Kinetics Run Prepare for the room temperature run by making up a reaction mixture of equal volumes of your cobalt complex solution and the nitrite/nitrous acid solution. Mix well. The time for your kinetics run should start when the solutions are mixed. Then pipet some of the reaction mixture into a cuvet. Suspend your cuvet in a room temperature water bath, to maintain a constant temperature. Record the temperature of the bath and monitor it during the course of the reaction. Set the wavelength of your spectrometer to 415 nm and calibrate it with a water blank. Record the absorbance of your reaction mixture every 3 minutes, until you are certain that the initial ligand substitution reaction is complete. Plot your data as you measure it, to help you judge. 35-40° Kinetics Run Make up a new reaction mixture and mix well. After noting the time, transfer some of the reaction mixture to a cuvet and suspend it in the 35-40° water bath. Record the temperature of the bath and monitor it during the course of the reaction. Set the wavelength of your spectrometer to 450 nm and calibrate it with a water blank. Record the absorbance of your reaction mixture every 3 minutes, until you are certain that the ligand isomerization reaction has reached equilibrium. Plot your data as you measure it, to help you judge. Measurement of A at infinite time Retrieve your reaction mixture from the 70° water bath. Transfer some of the mixture to a cuvet and measure the absorbance at 415 and 450 nm. Be sure to calibrate with a water blank, at each wavelength.
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