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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > July  >
In the Laboratory
A Student Laboratory Experiment Based on the Vitamin C Clock Reaction
Ed Vitz
Department of Physical Sciences, Kutztown University, Kutztown, PA 19530
Cover
July 2007
Vol. 84 No. 7
p. 1156
Abstract
We have adapted the vitamin C clock reaction to a student laboratory experiment in which the orders with respect to peroxide and iodide, the rate constant, and the activation energy are determined by the method of initial rates. Rates of the oxidation of iodide by hydrogen peroxide are determined by adding small quantities of vitamin C to solutions of hydrogen peroxide and iodide ion, so that the triiodide ion produced by oxidation of iodide is immediately consumed by the vitamin C. When all the vitamin C is depleted, the mixture turns black owing to the presence of the starch–triiodide ion complex. The rate is calculated as the ratio of the change in vitamin C concentration (which equals the change in hydrogen peroxide concentration) to the time required to reach the starch–triiodide ion endpoint. Rates are measured as a function of hydrogen peroxide and iodide concentrations and temperature. The pH effect is minimized by the addition of relatively high concentrations of acetic acid.
Supplement
Student instructions with details of solution preparation, Excel template, and WebCT prelaboratory questions (both as a native WebCT file and MS Word document) are available.
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Contents
  JCE2007p1156W.pdf
 
JCE2007p1156W.zip
Folder JCE2007p1156W containing JCE2007p1156W_1.doc and JCE2007p1156W_2.doc (Microsoft Word), and JCE2007p1156W.xls (Microsoft Excel)
More Information
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Citation
Vitz, Ed. J. Chem. Educ. 2007, 84, 1156.
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Keywords
Consumer Chemistry; First-Year Undergraduate / General; Hands-On Learning / Manipulatives; High School / Introductory Chemistry; Kinetics; Laboratory Instruction; Mechanisms of Reactions; Physical Chemistry; Rate Law
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History
Created:
Last Updated:
5/29/2007
6/7/2007
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