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Iodine Clock Reaction

Iodine Clock Reaction. We will begin by describing a proposed reaction mechanism for the iodine clock reaction. There are several variations to this reaction, the one in focus being the “iodate variation”. The reagents used are: Bottle A: Potassium iodate (KIO 3 )

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Iodine Clock Reaction

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  1. Iodine Clock Reaction • We will begin by describing a proposed reaction mechanism for the iodine clock reaction. There are several variations to this reaction, the one in focus being the “iodate variation”. • The reagents used are: Bottle A: Potassium iodate (KIO3) Bottle B: Sodium bisulfite(NaHSO3) Sulfuric acid (H2SO4) – This is a catalyst Starch indicator

  2. The overall process that takes place can be described by the following reaction mecanism(Arthur Moss, 1978): • Steps 1 and 2, commonly referred to as the Landolt and Duchman reactions respectively, are dominant so long as HSO3- is in excess. • Once it’s consumed, step 3 can no longer occur and an appreciable concentration of I2 becomes present.

  3. The starch indicator then rapidly combines with the iodine (triiodide, I3- , is actually present as well, in equilibrium with I2  and I-) to form the signature, deep blue, iodine-iodide-amylose complex  (John A. Church and Sanford A. Dreskin, 1968). • Iodine Clock Reaction

  4. Rate Law Expression • The rate law for this reaction will be in the form: Rate = k [IO3 ] x [HSO3 ] y where k is the rate constant for this reaction at a particular temperature, and x and y are the reaction orders for the iodate and bisulfite ions respectively. Since we are only looking at the effect of changing the concentration of the iodate solution (bottle A), the x-value is what you will determine in this experiment.

  5. Data • If you don’t have “good numbers” work with the following:

  6. Graphing Your Data When plotting reaction rate vs initial conc of A, compare your plot to the following to determine the order of the reaction.

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