I am just going to explain what I think happens in this reaction, and if anyone knows about this experiment and thinks I am doing something wrong, please let me know
So I take two beakers, beakers A and B.
I add the iodide ions solution (Potassium iodide I think) to beaker A with hydrogen peroxide. In beaker B, I add sodium thiosulphate solution with starch and then I mix beaker B with A. As soon as I mix them together, I start my stopwatch, and stop timing it when the solution turns from colourless to blue/dark colour.
The concentration of iodine added divided by the time taken gives me the rate of reaction of that concentration. Plotting a graph of rate of reaction against concentration, I can tell what order the iodine is.
That's what I know so far, one question I have is, since I add the beaker B to A, it is supposed to measure the iodine (being produced from the first reaction of iodide and hydrogen peroxide) reacting against thiosulphate ions. If I already add hydrogen peroxide and iodide ions together, doesn't iodine molecules already start being produced? So when I add the thiosulphate ions, won't there be iodine molecules already in the beaker which will react? So how is rate of reaction exactly measured?