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Molarity to Molality

  1. Nov 17, 2013 #1

    Qube

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    Gold Member

    1. The problem statement, all variables and given/known data

    The molality of an aqueous sodium nitrate solution is 2.14 m. What is the mole fraction of sodium nitrate?

    2. Relevant equations

    Molality = moles of solute / kg of solvent.

    Mole fraction of A = moles of A / total number of moles (in this case, moles of solute + moles of solution).

    3. The attempt at a solution

    Assuming we have 1 kg of solvent, we can assume we have 2.14 moles of NaNO3.

    Mole fraction of NaNO3 is therefore 2.14 / [(1000/18) + 2.14] = 0.0370.

    1000/18 because 1000 grams of water is present and there are 18 grams per mole of water. The grams cancel out and yield moles of water.
     
  2. jcsd
  3. Nov 17, 2013 #2

    Borek

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    Staff: Mentor

    Looks OK. You will get slightly better result by using more accurate molar mass of water.
     
  4. Nov 17, 2013 #3

    Qube

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    Gold Member

    I appreciate your consideration and helpfulness!
     
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