Question

A 2.50 g sample of a bronze gong was cut out and dissolved insuklfuric acid. The copper sulfate produced was mixed with KI toform CuI and the triiodide ion, I3-. The I3- ion was then titratedwith thiosulfate, S2O3 2-.

Cu+ 2 H2SO4 -> Cu SO4 + SO2 + 2 H2O
2CuSO4 + 5 I- -> 2 CuI + I3- + 2SO4 2-
I3- + 2S2O3 2- -> 3I- + S4O6 2-

If it took 31.5 mL of 1.00 M thiosulfate for this titration, howmany mols of copper were present in the original 2.50 g sample?