Question

I do not know how to find the moles of IO3- and [IO3-] so please if you guys can help figure it out!! thank you!

Experiment #3 Determination of an Equilbrium Constant Expression HA AK Part Il: Goal #2 Ak Soln A2 Soin B1 Soln A1 Soln 82 14.73ml .43 al 53ml I-10 ml intial buret volume 5.43ml 32.31m 32.10 m 13.90ml 17.58 ml 16.6tml 14.73 Vnl feal buret volume trant volume delivered 13.63 ml .1gx 16 Moles 5,0 Aoded Moles 10 Reacted 0 in Mature Soln C2 Soln D1 Soln D2 Soln C1 1.13 1.06 mL 100mt 1.19 mL 1.11 initial buret volume m 15.85 mL 2 6.62m 14.90mL final buret volume 12. L0mL mL 35.43 L a.05ML 3a.6am 26 79 ttrant volume delivered Moles SO Added Moles I0 Reacted pojn Mature

Answer 1

Even though it is not mentioned, this looks like an indirect determination of iodate, where there are two reactions involved:

IO₃^- + 5I^- + 6H⁺ → 3I₂ + 3H₂O

2S₂O₃^2- + I₂ → S₄O₆^2- + 2I^-

See that two moles of S₂O₃^2- react with each mole of I₂, and that 3 moles of I₂ come from one mole of IO₃^-. This means that every mole of S₂O₃^2- can be though as if reacting with 6 moles of IO₃^-originally in the sample. Actually, a sort of "total reaction" combining both steps can be written and explicitly shows this relationship:

KIO₃ + 6Na₂S₂O₃ + 6H⁺ → 3S₄O₆^2- + I^- + K⁺ + 12Na⁺ + 3H₂O

This means that the number of moles of iodate is 1/6 number of moles of thiosulfate you used in your titration. For solution A1, this means there were: 4.18x10^-4 moles/6 = 6.97x10^-5 moles. In order to calculate the concentration of iodate, you need to divide the number of moles by the volume of sample you used (it isn't shown in the picture) in units of LITERS, since molar concentration represents the number of moles per liter.

The number of moles of the following solutions can be calculated in the exact same way. The concentration of the  S₂O₃^2- solution is needed to calculate the number of moles of  S₂O₃^2- added, so they are up to you! If in doubt, don't hesitate to write in the comments section.