Week 8: 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		Prelab Problems 1. Given your knowledge of the mechanisms of the ligand substitution and isomerization and the relative rates of the two reactions, draw a graph of how you would expect absorbance at 415 nm to change with time during the course of the entire 2-step reaction. Mark the time when the initial substitution reaction is complete. Draw a second plot showing how the absorbance at 450 nm would change with time for the same reactions, again marking the time when the initial substitution reaction is complete. 2. The rate of reaction of [Co(NH3)5(H2O)]3+ and nitrite ion was monitored at 25°C under pseudo first order conditions and the following observations were made: [NO2-] [HNO2] k' 0.05 M 0.0063 M 2.6 s-1 0.10 0.0125 10 0.20 0.025 42 0.20 0.0125 23 0.20 0.0063 10 What is the reaction order with respect to nitrite and nitrous acid, based on these data? Show simple calculations to support your answer. 3. The following absorbance vs. time data were obtained at room temperature and at 412 nm. Using this data, determine the pseudo first order rate constant for the ligand substitution reaction in min-1 and s-1. The final absorbance of the reaction mixture was 0.89. time A at 412 0 min 0.072 4 0.169 8 0.21 18 0.295 24 0.33 33 0.355 36 0.368 4. Calculate the concentration of [Co(NH3)5(H2O)]3+ in your reaction mixture and compare to the concentration of NO2-, which is approximately 0.5 M. What does this lead you to predict about the rate law of the reaction under these conditions?
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