Full Lab Manual
Introduction & Goals
Chemistry & Background
In Your Write-up
1. For the region of the spectra shown in the Figure on page 127 in your lab manual, what is the wavelength of maximum absorbance, λmax, for the three complex ions: Co(NH3)5(H2O)3+, Co(NH3)5(ONO)2+, and Co(NH3)5(NO2)2+? To what color of light does each λmax correspond? What is the color of a solution of each complex ion? (You can use the Spectrum applet to help you answer this question.)
2. Given your knowledge of the mechanism of the ligand substitution and isomerization and the relative rate 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 two-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.
3. 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:
What is the reaction order with respect to nitrite and nitrous acid, based on these data? Show simple calculations to support your answer.
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