Investigating the rate of reaction between peroxydisulphate(VI) ions and iodide ions

The first 200 words of this essay...

In this investigation I will be looking into:

* The effect of changing the concentration of reactants upon the rate of reaction. I can calculate the order of the reaction with respect to the variable reactant (potassium iodide ions), and then I can use the known orders of other reactants to obtain the rate equation. From the rate equation I can then work out the overall order of reaction.

* The effect of changing temperature upon the rate of reaction. I can find the rate of reaction for different temperatures and substitute these into the rate equation, allowing me to work out a value of k for each temperature. These k can be used to draw graphs from which I can calculate the activation enthalpy.

Section 1 - Theory

The iodine clock reaction is a two stage reaction. In the first (R1), peroxydisulphate (VI) ions react with iodide ions to form sulphate (V) ions and iodine:

Both reactants and the sulphate ions are colourless. To measure the initial rate of this reaction, the colour of the iodine produced can be followed. The colour change can be detected more clearly by adding starch to the