Iodine clock kinetics HELP!!!!!!

Question

In the iodine clock reaction involving persulfate and potassium iodide: why is the experimental method of determining rate law called 'method of initial rates' when acutally the 'average' rate is measured? How does 'intial' come into play?

Also, is this calculation correct:

rate = (volume of thiosulfate added* concentration of thiosulfate added)

(2*total volume of reaction mixture*time for blue colour)

Regarding rection mechanism, is the reaction mechanism of this iodine clock just simply the three equations? The first being KI reacting with persulfate

Second: iodide reacting with thiosulfate

third: iodine freed from first reaction now reacting with starch indicator to form blue complex?

Or is the reaction mechanism harder to determine?

Answer 1

http://en.wikipedia.org/wiki/Iodine_cloc...

SEE?EASY!