analysis of chlorine bleach

why does everyone expect others to know everything about every procedures of his every experiment?
no, we're not your teachers or classmates. we don't know what experiment you're doing. we don't know what procedures or reagents you've adopted.

we're considerate, so we answer your questions. so please, be considerate. list out any information you may find necessary for us to understand your situation and problem.

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since your'e not providing procedure, i can only guess.
1.
it's a back-titration of iodine produced by hypochlorite with thiosulphate.
it's to turn all hypochlorite into iodine for the titration with thiosulphate following.

2.
where did you add your sulphuric acid????? i have no idea.


2010-10-12 23:11:37 補充：
1. in addition to above, to make sure that all iodine remains dissolved as triiodide ion.
2. to promote complete reaction of hypochlorite, forming iodine.
2H(+) + ClO(-) + 2I(-) ------> Cl(-) + I2 + H2O