[newbie!]

1.)   Determine the amount of copper in a copper supplement, which contains approximately 100 ppm (m/m) of copper sulphate. The method uses iodide to reduce the copper from divalent to monovalent copper. The resulting iodine is subsequently during the titration reduced again with thiosulfate.
a)   Give both redox reactions and calculate the stoichiometry
ok i have:
 Cu2+ + I- -> Cu+ + I(s)
I(s)  + Na2S2O3 -> I- + ?

b)   calculate the amount of food supplement you need to weigh into an Erlenmeyer for digestion before titration using a 0.01 M thiosulfate solution, when you have a 10 mL burette available. Remember the error of the burette.
ok i have  no idea.
we are titrating the 0.01M thiosulphate with what? iodine? or copper sulphate?
i'm assuming copper sulphate? because otherwise i dont see its relevence in the question? (unles "Determine the amount of copper in a copper supplement, which contains approximately 100 ppm (m/m) of copper sulphate" is a question on its own? but really that should be made clearer) but then it does say that I- gets titrated with thiosulphate.
... *delete me*?

[Borek]

http://www.titrations.info/iodometric-titration-copper