MAKING THE MOST OF THE IODINE CLOCK REACTION IN FRESHMAN CHEMISTRY LAB

Authors

Richard Willis Schmude Jr., Gordon State College, Barnesville, GA, 30204Follow
Taylor Karoline Taylor author2_suffix, Gordon State College, Barnesville, GA, 30204Follow

Abstract

The KIO3 + NaHSO3/Starch Reaction (or Iodine Clock Reaction) may be used in illustrating some kinetics concepts to first-year chemistry students. In a typical laboratory session, the student mixes different concentrations of a KIO3 solution with a NaHSO3/Starch solution and then times how long it takes the mixture to turn purple (the reaction time.) There is more potential in using this experiment to teach the concepts of kinetics and initial rates. In this study, the concentration of each reactant affecting the reaction time was examined. Furthermore, how temperature affects the reaction time was also examined. Finally, the pH of the reaction mixture was measured from the time the two solutions were mixed until the solution turned purple. The pH dropped from 4.4 to 3.4 when it turned purple. It is concluded that the reaction time is inversely proportional to the concentration of KIO3 and NaHSO3 solutions. It is also concluded that the reaction time drops as the temperature rises. Additionally, the pH of the reaction mixture should be measurable at different temperatures. This information enables one to compute the initial rate of the reaction and, hence, determine the rate law and the value of the activation energy.

Acknowledgements

The writers are grateful to Alan Scouten for his help and support.

Recommended Citation

Schmude, Richard Willis Jr. and Taylor, Taylor Karoline author2_suffix (2025) "MAKING THE MOST OF THE IODINE CLOCK REACTION IN FRESHMAN CHEMISTRY LAB," Georgia Journal of Science, Vol. 83, No. 1, Article 66.
Available at: https://digitalcommons.gaacademy.org/gjs/vol83/iss1/66