Investigating the Kinetics of the Reaction Between Iodide Ions and Peroxodisulphate (Vi) Ions (Entire Plan)

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Investigating the Kinetics of the reaction between Iodide ions and Peroxodisulphate (VI) ions

By the use of an Iodine clock reaction I hope to obtain the length of time taken for Iodine ions (in potassium iodide) to react fully with Peroxodisulphate ions (in potassium Peroxodisulphate). I will do three sets of experiments changing first the concentration of iodide ions, then the concentration of Peroxodisulphate ions and finally the temperature of the solution in which the reaction is taking place. From these results, I hope to draw conclusions as to the effects of these changes to the environment of the reaction on the rate and also determine the order of the reaction and the activation enthalpy.

Background information
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In terms of log to the base 10 this is:

log k = log A –Ea/ 2.303 RT

Reaction between Iodine ions and peroxodisulphate ions

S2O82-(aq) + 2I-(aq)  2SO42-(aq) + I2(aq)

In order to make the reaction clearer, during my experiment I will add starch and a small known amount of sodium thiosulphate (to act as a queching agent). The thiosulphate ions turn iodine back to iodine ions:

2S2O32-(aq) + I2(aq)  S4O62-(aq) + 2I-(aq)

Which means that no starch-iodine colour will appear until all the thiosulphate has been used up. The amount of time taken for this occur (and the reaction to suddenly turn blue) is the same amount of time for the reaction to produce the equvilant amount of Iodine.


(For making up solutions) weighing boats scales Beaker (150cm3)
3 Volumetric flasks (250cm3)
Distilled water
Glass rod
(for concentraion and temperature change experiments)
4 thermometers (0-110ºC)
A large number of boiling tubes (roughly 50 depending on repeats)
5 Burettes with funnels for filling
5 Clamp stands (for burrettes)
(for temperature change only)
Two large beakers (400cm3)


Freshly made starch solution
Pottasium Iodide (made to solution with conc. 1.00 mol dm-3)
Pottasium peroxodisulphate (made to solution with conc.
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