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Homework Help: Chemistry: acid base moles EMERGENCY PLEASE HELP!

  1. Apr 21, 2010 #1
    1. The problem statement, all variables and given/known data

    Hi. I'm reaady to panic right now so if anyone could please take the time to answer my question I would HUGELY appreciate it!!! I seriously need to get this done soon as I also have a test tomorrow and i just want to cry because i'm getting nowhere...

    We did a lab experiment which involved 50 mL of 1.02 Molar H3PO4. The density was given to be 1.05 g/mL.

    We also had 45 mL of 1 Molar Na2CO3 with a density of 1.10 g/mL.

    We were asked to find the mass of both solutions. I got 52.5 g of H3PO4 and 49.5 g of Na2CO3.

    Our professor gave us the value that there is 45 mmoles of limiting reagent. And I would assume the Na2CO3 is the limiting reagent because there is less of it.

    But HOW IN THE WORLD did he get 45 mmoles????

    This is how i'm trying to do it:

    (49.5 g Na2CO3)/ (106 g Na2CO3)= .467 moles, or 467 mmoles of Na2CO3, and since there are the same number of moles of CO3 2- as Na2CO3, the mmoles of CO3 2- should also be 467 mmoles.

    why am i SOOOOO far off????

    PLEASE HELP!!!!!!! i have a million questions to do on this lab and i can't even understand why my numbers are the way they are so i can't even start TRYING to answer the questions because i'm so confused...
    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 22, 2010 #2
    OMG nevermind....a million hours later i looked at this again, and i have no idea what i was thinking earlier...

    I figured it out...this is why it's good to get a good night's sleep...after a while, even simple things look impossible!!! hahahah
  4. Apr 22, 2010 #3


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    Staff: Mentor

    For those looking later at the thread - mass of the solution is NOT mass of the reagent dissolved.
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