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1. The problem statement, all variables and given/known data

I have to determine the concentration of a sodium thiosulfate solution used to titrate a potassium iodate solution. The only variable that is known is the concentration of the potassium iodate solution, 0.01 mol/L. There is 20 mL of 0.01 M potassium iodate mixed with 25 mL of water, 2 mL of 3M H2SO4 and 3 mL of 1M KI. This is the analyte. The titration required 12.35 mL of the sodium thiosulfate solution to reach endpoint.

2. Relevant equations

here is the reaction equation for the titration (note: K is omitted because it plays no role in the reaction):IO3-(aq) + 6 S2O32-(aq) + 6 H+(aq)→ I-(aq) + 3 S4O62-(aq) +3 H2O(l)

3. The attempt at a solution

In order to determine the molarity of sodium thiosulfate, the molarity of the 50 mL potassium thiosulfate must be determined, then the amount of moles can be determined from that and using stoichiometric ratios, the moles of sodium thiosulfate can be determined and so forth... I have tried to use the equation C1V1=C2V2 but i get a weird answer:

C2= (0.01M)(1L)/(0.05L) = 0.2 M.

There is no way this can be correct as why would the concentration in a diluted solution be greater than the initial concentration?

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# Homework Help: Electrochemistry Lab

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