13b- Iodine Clock reaction

Question 1

Describe the method used in the iodine clock reaction used to determine the rate equation

Answer 1

1- measure out a set amount of a known conc of potassium Iodide (KI) using a burrette into a beaker

2- add set amount of known conc of Sodium Thiosulfate- Na2S2O3 - followed by few drops of starch solution

3- add a set amount of known conc Sodium peroxidisulfate - Na2S2O8 -and start stopwatch as soon as 2 solutions have been added
4- stop stopwatch when blue colour appears + record time
5- repeat using different quantities of = peroxidisulfate, Iodide and Thiosulfate ions and

Question 2

What is going on in solution of CP13B between : Peroxidisulfate , Iodide and Thiosulfate ions

Answer 2

Peroxidisulfate ions -
S2O8(2-) react with Iodide ions - I(-)
To form sulfate ions and iodine
S2O8(2-) + 2I(-) = I2 + 2SO4(2-)

The iodine produced is reduced back to Iodide by the Thiosulfate ions -
S2O3(2-) + I2 = 2I(-) + S4O6(2-)

When all the thiosulfate ions have been used up there iodine remaining reacts with starch solution to produce blue / black colour

Question 3

What kind’ve table will you make in the iodine clock reaction - 13b
Where your trying to determine rate equation

Answer 3