[dmp90]

I just performed a lab in my chemistry class today and we have to determine the percent of sodium carbonate in an unknown sample of soda ash. The first part of the lab involved standardizing the titrant, sulfuric acid. We had to transfer 10.00 mL of 6M sulfuric acid into a 500.00 mL volumetic flask.Then, 3 samples of sodium carbonate were weighed out and put into 3 different flasks. A titration followed this. My data is as follows:
-Amounts of Na2CO3 weighed out:
Flask 1: 0.5299 g
Flask 2: 0.5012 g
Flask 3: 0.5332 g
- Amounts of H2SO4 used:
Flask 1: 21.00 mL
Flask 2: 19.80 mL
Flask 3: 20.60 mL
For this part of the lab, I have to find the molarity of H2SO4 in order to get the average molarity of H2SO4. I believe I will need this in order to find the percent of Na2CO3 in the unknown soda ash sample for the second part of the lab. I started my calculation of the molarity, but I am not sure if I am doing it correctly. Can someone tell me if I am?
-Molarity of H2SO4 in flask 1: *note: each mole of Na2CO3 reacts with 2 moles of H+
0.5299 g Na2CO3 * (1 mol Na2CO3/105.99 g Na2CO3)*(2 mol H2SO4/1 mol Na2CO3)*(1/0.02100 L H2SO4)= 0.4761 M

[Borek]

each mole of Na2CO3 reacts with 2 moles of H+

That's right, but does it mean

(2 mol H2SO4/1 mol Na2CO3)

[dmp90]

Yes that's exactly what I meant. This is so because of the overall reaction is:
CO3 2- + 2H+   H2O + CO2 (g)