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Using the iodine clock method to find the order of a reaction.

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Using the iodine clock method to find the order of a reaction. Requirements: * 0-110 thermometer * boiling tubes (5) * test-tubes * burettes (or graduated pipettes 1cm , 2cm and 5cm ) * potassium iodide solution, 1.00 mol dm (15cm ) * potassium peroxodisulphate(VI) (K S O ) solution, 0.0400 mol dm (10cm ) * sodium thiosulphate (Na S O ) solution, 0.0100 mol dm (10cm ) * freshly made starch solution (5cm ) * stopwatch Introduction: This reaction takes place when peroxodisulphate(VI) ions and iodide ions react together in solution to form sulphate(VI) ions and iodine. Here is a clear view of the balanced equation representing this reaction; S O (aq) ...read more.


In this experiment I will be using this clock method in order to find out how the reaction rate depends on the concentration of iodide ions in the reaction mixture. You may find it useful to plot your results on a graph via computer, but I have learnt that it's a much better idea to draw graphs by hand, as computers can't always include all the vital information. Method: 1: Firstly I made up the reaction mixture no.1 from the table below, and measured how long it took for the blue-black iodine-starch colour to appear. I then continued this with the other mixtures in the table, which only differ in the concentration of iodide ions, the water is added to keep the volume at a constant. ...read more.


Time 1 1.08 2 1.03 3 1.53 4 3.18 5 8.04 Finding the order of reaction: Using the results above I can now perform the calculations. To find the order of the reaction with respect to iodide ions, I will have to know how the initial rate of the reaction varies with iodide ion concentration. In order to do this I will have to do the following; * Work out the amount of I produced before the blue-black colour appears. * Use this amount of I and the clock time to work out the initial rate of reaction for each mixture. * Plot a graph of the initial rate of reaction against [I ]. * Use the graph to determine the order of the reaction with respect to I ions. ...read more.

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