A Student Laboratory Experiment Based on the Vitamin C Clock Reaction.

• Autores: Ed Vitz
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 84, Nº 7, 2007, págs. 1156-1157
• Idioma: inglés
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• Resumen

  • 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.