IODINE CLOCK REACTION SERIES

This instant darkening effect, reminiscent of the sudden onset of night in Egypt, gave this reaction its poetic name of “Egyptian Night. When the forming iodine has already reacted with all of the available sodium thiosulfate, it begins to react with starch, forming a dark-blue starch-iodine complex. The solution remains clear because the forming iodine reacts with sodium thiosulfate: Hydrogen peroxide oxidizes iodide ions to molecular iodine: Several oxidation-reduction reactions take place in the solution, which can be described as follows Colorless solutions are mixed and, following a short pause, the liquid rapidly turns dark blue, almost black. This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not. The “Iodine Clock” reaction (sometimes called “Egyptian Night”) is an oxidation-reduction reaction.

The volume of solution C is variable – adding more or less of solution C will affect the speed of the reaction. The greener version of the Clock Reaction also eliminates the use of 1 kg potassium iodide (8 gal. The experiment: combine 100 mL of solution A and 50 mL of solution B in a pitcher. a reduction in waste from 29.5 gallons to 7.5 gallons. Preparing a hydrogen peroxide solution (solution C): combine 400 mL distilled water, 100 mL 15% hydrogen peroxide solution, and 5 mL concentrated sulfuric acid in a 500 mL beaker. Add 500 mL distilled water and stir thoroughly. Preparing a solution of sodium thiosulfate and potassium iodide (solution B): combine 1 g sodium thiosulfate and 5 g potassium iodide in a 500 mL beaker. Add 400 mL freshly-boiled water and stir. The 'clock' reaction is the reaction of a very small amount of S 2 O 3 2-(thiosulfate) with the I 2 produced in the primary reaction: Equation 2 The clock reaction will signal when the primary reaction forms a specific amount of I 2.

Preparing a starch solution (solution A): Combine 5 g starch and 100 mL cold distilled water in the 500 mL beaker. starch, so no color change is observed until the thiosulfate is completely used up. Increasing chlorate and acid concentration reduces the induction period. This is the first example of a clock reaction using chlorate as a reagent.

100 mL 15% hydrogen peroxide solution A clock reaction produced by mixing chlorate and iodine solutions in perchloric acid media is reported.

IODINE CLOCK REACTION SERIES

The aim in this particular activity is to create a series of solutions for which the clock period has been predicted based upon analysis of experimental data which the pupils will generate. The rate of reaction is to be determined with a stopwatch.

The clock period (the time from mixing to colour change) can be changed by varying the concentrations of the reactants. The color change occurs when I 2 reacts with starch to form a dark blue iodine/starch complex. When a solution of hydrogensulphite (or bisulphite) ions (HSO 3-) is mixed with a solution of iodate (IO 3-) ions and a starch solution, the mixture remains colourless for a time and then suddenly turns blue. The activity described here is based on the so-called iodine clock reaction. This sudden and unexpected nature of the change gives clock reactions their charm and visual appeal. In a 600 mL beaker, put in 20 mL 0.25M NaHSO 3, and 130 mL H 2 O. Typically after a clock reaction has been started there is a period during which no noticeable change takes place and then a change (often in colour) occurs. Procedure: In a 400 mL beaker, add 100 mL 0.1M KIO 3, 5 mL 1 starch, and 100 mL H 2 O. In an iodine clock reaction, colour changes after a time delay. I have been investigating the iodine-clock reaction for my chemistry project. Clock reactions are amongst the most dramatic and visually pleasing chemical demonstrations. Solutions Solution A: 2gm KIO3 in 1 liter H2O Solution B: Dissolve 2gm soluble starch in 500ml boiling water, add 0.4gm NaHSO3 + 5ml 1.0M H2SO4, then bring.

Iodine clock reaction