What does the iodine clock reaction show?

The “clock reaction” is a reaction famous for its dramatic colorless-to-blue color change, and is often used in chemistry courses to explore the rate at which reactions take place. The color change occurs when I2 reacts with starch to form a dark blue iodine/starch complex.

What are the two reactions that occur in the iodine clock reaction?

There are two reactions occurring in the solution. In the first, slow reaction, the triiodide ion is produced . H2O2(aq) + 3 I-(aq) + 2 H+ → I3- + 2 H2O. In the second, fast reaction, triiodide is reconverted to iodide by the thiosulfate.

What is the order of iodine clock reaction?

where, k is the rate constant (or rate coefficient); l and m are the orders of the reaction with respect to the reactants A and B, respectively; and the sum l + m is the overall reaction order.

How does an iodine clock work?

In an iodine clock reaction, the blue color is due to the starch–iodine complex, but the compound that is “trapped” by thio sulfate ions is iodine itself, which is reduced back to colorless iodide ions.

What are the ingredients in the iodine clock reaction?

This reaction starts from a solution of hydrogen peroxide with sulfuric acid. To this is added a solution containing potassium iodide, sodium thiosulfate, and starch.

What causes the iodine clock to turn blue?

In the Landolt iodine clock reaction the sudden change from colorless to blue-black indicates the bisulfite ion has been consumed.

How is the time determined in the Landolt iodine clock?

In this demonstration the time required for the sodium bisulfite ion to be consumed by the potassium iodate is determined. This requires a “signal” that indicates that the species has been consumed. In the Landolt iodine clock reaction the sudden change from colorless to blue-black indicates the bisulfite ion has been consumed.

How to measure the rate of formation of iodine?

One creative way of measuring the rate of formation of iodine is to couple the reaction in which the iodine is formed (Reaction 1) with a much faster reaction that consumes all of the iodine (Reaction 2) I 2 (aq) + 2 S 2 O