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Homework Help: Finding molarity of substance

  1. Sep 15, 2013 #1
    1. The problem statement, all variables and given/known data

    Glacial acetic acid has a density of 1.05g/ml and contains 99.51%acetic acid (CH3COOH) by mass. Calculate the molarity of glacial acetic acid.

    So, this is a question in my pre-lab that doesn't even count. But, I still want to get it because we have similar questions in exams.

    I'm blocked at the first step:
    What is molarity?
    Is is the total number of moles? or just the number of acetic acid moles?
  2. jcsd
  3. Sep 15, 2013 #2
  4. Sep 15, 2013 #3
    It doesn't really help. I'm asking to know if glacial acetic acid is a solution per se. What is the small percentage that makes CH3COOH account for 99.51%? And is that substance taken into any account when you do the calculation of molarity.
  5. Sep 15, 2013 #4
    Did you look at the definition of molarity? We aren't concerned with 0.49% but that will be used when calculating molarity. Have a look at the definition, you will get some idea to begin with.
  6. Sep 15, 2013 #5


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    Staff: Mentor

    Also, if you take a look at the definition, you can apply it even to pure water - that's a very similar situation.
  7. Sep 15, 2013 #6


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    Homework Helper

    Do you know how to find the number of moles of CH3COOH in 1000 mL of glacial acetic acid? That is the same as the molarity.
    What is molarity?
    moles of constituent (CH3COOH here)/ Liters of solution (glacial acetic acid here)
    Is is the total number of moles? or just the number of acetic acid moles?
    Only acetic acid.
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