Finding Na2S2O3 molarity from iodometric titration of copper in brass

[Puchinita5]

Homework Statement

I am so confused.

I am doing a "Iodometric Titration of Copper in Brass" lab.

We first made a thiosulphate solution by mixing 500 mL water, 12.5 g of Na2S203 * 5H20, and .05 g Na2CO3. This solution is "supposed" to come out to be about 0.1 M. My actual measurements were about 12.5002 g of Na2S2O3*5H20 and .0502 g Na2CO3.



We then made an approximately 0.02M KI03 solution where I mixed 2.1400g KIO3 dissolved in water to 500mL.

We then added 25.00 mL of this KIO3 solution to a flask, as well as 1mL concentrated HNO3 and 1g of KI. Then we titrated this with our Na2S2O3 solution.

I need to figure out the molarity of my Na2S2O3 (thiosulphate) solution, but I don't know how.

Someone please help my lab report is due tomorrow and I don't even know where to start and I'm starting to panic. :(


I can't do the rest of my report until I can figure this out.

Homework Equations

The Attempt at a Solution

 

[Borek]

Start with reaction equations.

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

 

[Puchinita5]

Yes! I didn't know these equations and my google searches were not helping me at all. This definitely clears up a lot!

Thank you! crisis averted! :)