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This General Chemistry laboratory experiment studies the kinetics of the reaction between household bleach (NaOCl) and the food dye F.D.&C. #40, also known as Allura Red. Students follow the reaction spectroscopically, utilizing the Beer-Lambert law to determine the concentration of Allura Red as the reaction proceeds. Concentration terms are graphed versus time and the reaction order with respect to Allura Red is found by determining which version of the integrated rate laws yields a straight line. A pseudo first-order approximation is used to find the order with respect to bleach. The rate constant is determined using the rate law and initial concentrations. At the end of the experiment, all waste can go down the drain.
Data analysis and graphing for this experiment can become tedious if a spreadsheet program isn't utilized. Additionally, many General Chemistry texts do not cover pseudo first-order approximations and students may find the data analysis confusing if they aren't properly prepared beforehand. This experiment is most effective if students have performed the Spectrophotometric Analysis of a Food Dye experiment previously utilizing the same reagents and equipment.
Summary prepared March 2012 by Dr. Deborah Exton, University of Oregon.
Exton, D. B. General Chemistry in the Laboratory, 2/e, McGraw-Hill Learning Solutions, ISBN 0-07-804433-5., Print