Work in groups of two to investigate the kinetics of reaction between aqueous chlorine and bromide. Use the paper by Kumar and Margerum[1] that we discussed in class as a guide.
A. Using the HP 8452A Diode Array Spectrophotometer, investigate the reaction under alkaline conditions (i.e., pH ~10.5 to pH ~13.5) and at a temperature of 25ºC. You may use a single fixed initial bromide concentration of 0.100 M and add small amounts of NaOCl (~ 0.5 mM) so that the reactions are pseudo-1st order. Use whatever wavelength or wavelengths you think appropriate. You may use the solutions that I prepared and/or you may prepare your own. Run at least a dozen experiments under differing pH/hydroxide concentrations. Use these data to determine a rate law, employing graphical representations whenever appropriate. What does this tell you about the nature of the reaction? Compare your rate law with the ones presented in Kumar and Margerum. Do you agree with these authors? Prepare a concise report summarizing your findings.
B. Expand upon your studies in part “A” by determining the impacts of varying temperature. Run several sets of experiments under temperatures that range from ~5ºC up to ~35ºC. Use these data to determine the activation energy. What does this tell you about the nature of the reaction? Does the mechanism change as temperature changes? Prepare a concise report summarizing your findings.
Assigned: 27 Mar 08
Part A Due: 8 Apr 08
Part B Due: 10 Apr 08