Anyone good at chemistry?

[GhoSt]

Hey all, I am pretty average at chemistry due to my workload in other subjects taking priory. Anyway I have a practical investigation I have to carry out and if anyone could drop some knowledge on the topic that would be great.

Ok the investigation I am doing is to evaluate the trends of the concentration of hyperclorite ions in household bleach after timed exposure to air (5 samples, interval of roughly 4 days). I know I will do this by standardizing Thiosulphate with permanginate  and titrating with that to find the concentration of liberate iodine (when OCL- is reacted with KI and acid). And my hypothesis is obviously rise in length of exposure decreases the concentration of OCl-.

Onto what I need your guys help with, why is this so? Reaction with oxygen? Evaporation? Someone told me it was evaporation, proved with this equation     3 NaClO → NaClO3 + 2 NaCl... is that correct?

Also I need to get titre values between the range of 10-20mL, how would I go about standardizing the bleach samples to get the correct dilutions without taking a sample titration of the un-diluted bleach itself?

So if you can chip in anything at all that can help me out, or link me to some info, it would be greatly appreciated since this counts towards my end of year enforcement.

Thanks for your time,
   Steve

[FOOKz™]

idk if you feel comfortable boiling bleach..... but figure out a way to get the water our of it....

100% isopropyl alcohol mixed with diluted bleach will evaporate the water and reduce the boiling point of water. So if you wanted to get some pure hypochlorite i think thats the way to do it safely.

Since bleach's active ingredient is a type of salt it does not evaporate well under normal conditions.

If you wanted to do calculation before testing just use molar mass to help determine what concentrations you have to have in order to get the best equivalence point with the reaction and testing the reaction.