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Homework Help: Molar Mass calculation

  1. May 16, 2009 #1

    lha08

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    1. The problem statement, all variables and given/known data
    I'm having a lot of trouble trying to find the molar mass of (HOCH2CHOH)CH2O2


    2. Relevant equations



    3. The attempt at a solution
    Do i have to multiply the molar mass inside the bracket (HOCH2CHOH) by the outside CH2O2?
     
    lha08, May 16, 2009
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  3. May 16, 2009 #2

    symbolipoint

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    You are asking about how to find the mass of one mole of the compound. Maybe you have some difficulty with the text-based way to express the compound? What is the exact name of your compound? Maybe an empirical formula would make the method more apparant to you.
     
    symbolipoint, May 16, 2009
  4. May 16, 2009 #3

    lha08

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    The compound's name is glycerol
     
    lha08, May 16, 2009
  5. May 16, 2009 #4

    symbolipoint

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    Thanks. This makes the identity of the compound plain. Now, does the name tell you anything about the structure? Maybe not. Another name for glycerol is 1,2,3-propanetriol. If you know enough about simple naming of organic compounds, you could make sense of that; but since you asked, you did not yet progress that far.

    A good wikipedia article showing the structure is this:
    http://en.wikipedia.org/wiki/Glycerol
    A molecular formula is also given.
     
    symbolipoint, May 16, 2009
  6. May 17, 2009 #5

    Borek

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    Staff: Mentor

    No. Content of parentheses is to be taken as many times, as number after the closing parenthese tells. No number - no multiplication.

    Ca3(PO4)2 - means 3 atoms of Ca and 2 groups of 1 atom of P and 4 atoms of O.

    Sometimes you may want to use parentheses to show that some group of atoms is to be treated separately for some reason, but this is not a formal notation.

    (Na)Cl - 1 atom of Na, 1 atom of Cl. Parentheses not necesary.

    In this case looks like they put the parenthese only to trick you into thinking there is more to it. There is no.
     
    Borek, May 17, 2009
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