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Stoichiometry

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Problem: Iodine is present in Chilean saltpeter as iodate anion (IO3-). The amount of iodate anion in a particular sample may be determined by dissolving the sample and then reacting the IO3-(aq) with excess aqueous sodium bisulfite (NaHSO3(aq)) via: 2 IO3-(aq) + NaHSO3 (aq) -----> I2(aq) + Na+(aq) + 5SO4-2(aq) + H+(aq) + H2O(l) . (1)

The I2(aq) produced above is then reacted with (excess) aqueous potassium iodide (KI(aq)):
KI(aq) + I2(aq) -----> K+(aq) + I3-(aq) . (2)

The I3−(aq) is then reacted completely with a stoichiometric amount of aqueous
sodium thiosulfate, Na2S2O3 (aq):
2 Na2S2O3(aq) + I3-(aq) -----> Na+(aq) + I-(aq) + S4O6-2(aq) . (3)

First, write out and balance each of the partially balanced reactions (1, 2, & 3) above.

Suppose a 80.680 g sample of Chilean saltpeter produces sufficient I2(aq) to react completely with 5.128 g of Na2S2O3 . Calculate the mass percent of iodate anion, IO3- , in the saltpeter sample.

*If you can't read the charges, I have attached the Word document of the problem.
*Please show all steps and calculations

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