[rob11]

Ok any help not this would be appreciated, the question is:

2. Using stoichiometry , calculate the number of moles of I₂ released and therefore the number of moles S₂0₃^2- which must have been used in the titration

I came up with the chemical equation but unsure where to proceed from here.

I₂ + 2S₂0₃^2- ------> S₄O₆^2- + 2I^-

Can anyone point me in the right direction?

[AWK]

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

[mz4000]

Alright well first off you are going to need the volume of S2O3 you used in the titration in ml.  To do this subtract the starting point from the ending point.  Next you will need to multiply by the density of S2O3.  This will take you to the number of grams used.  Then take the grams value and divide by the molecular weight of S2O3.  So now you have the number of mols of S2O3 used in the titration.