Dec 15, 2015
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  1. Pre-Medical
Okay so I got this question on my practice exam and there is a conversion factor that I do not understand or better I don't know where they got it from if someone knows please explain

consider the unbalanced reaction Na2CO3 +HCl--> CO2 + H2O + NaCl
for this reaction, how many ml of a 2M solution of Na2CO3 are required to produce 11.2L of CO2 at STP?

1. I know i gotta balance the eq
2. Use stp at 224 L
3. convert to moles of Co2
4. then moles if Na2CO3
5??? this is where i'm stuck the explanation states that for ever 1mol of Sol'n there are 2moles of Na2Co3 where is the 2 coming from? I don't have a 2 as a coefficient where I balance it i have a 1:1 ratio
if you get my question and understand my dilemma please explain. thanks
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Jun 21, 2015
I think in #5, you should have written, in every LITER of solution, there are 2 moles of Na2CO3. Because you are given a 2M solution. They chose 1 liter has 2 moles because they are nice whole numbers. (There may be a typo in your text)

11.2L of CO2 is half a mole, therefore you need half a mole of Na2CO3, because we found a 1:1 ratio in the balanced equation. If 1 liter has 2 moles, then 250mL has a half mole..
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