[goatknee]

We did a lab and I'm wondering if my calculations are on track.

First we made a solution of KIO₃ (0.9034g) and 250mL water, which was used in a buret.

In a Erlenmeyer flask we had 15.00mL of an unknown ascorbic acid solution, 7.5mL of 1M HCL, 1.5g potassium iodide (KI) and a dropperful of 1.5% starch solution.

Lets say the flask was fully titrated with 23.90mL of the KIO₃ solution from the buret.

Here are my calculations:
Molarity of KIO₃: 0.9034g x 214g /.25L = 0.01689mol

Moles of IO₃^- used: 23.90mL / 1000mL x 0.01689mol = 0.0004037mol IO3-

Moles of I₃^- produced: 0.0004037mol IO₃^- x (3 mol I3- / 1 mol IO₃^-) = 0.001211mol I₃^-

Moles of ascorbic acid present: 0.001211mol I₃^- x (1 mol ascorbic acid/1 mol I₃^-) / .015L = 0.08074mol

Mass of ascorbic acid present in solution: 0.08074 mol ascorbic acid x (176g/1 mol ascorbic acid) = 14.21g

Percent of ascorbic acid in unknown solution if assumed density is 1.00g/mL: 14.21g/15.00g x 100% = 94.73%

I feel like I am missing a valuable step in my calculations somewhere. Any thoughts?

[Borek]

Moles of ascorbic acid present: 0.001211mol I₃^- x (1 mol ascorbic acid/1 mol I₃^-) / .015L = 0.08074mol

If you divide by volume, you are not getting number of moles, but the concentration.

[goatknee]

Doh! Thanks, okay so I'm definitely adding an extra step there. Its a straight mole ratio so the moles of ascorbic acid would be the same as I₃^- which would be 0.001211

so then would I divide by volume in the next question where I'm trying to find the mass of acid present in the solution? 0.001211 / 0.015 x 176g ?

[Borek]

Mass is just number of moles times molar mass.

What is the question?