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Homework Help: Finding Mass of Solute

  1. Nov 4, 2009 #1
    1. The problem statement, all variables and given/known data
    I'm doing an experiment for Science Fair, and one of the parts requires that I know the mass of a solute (NaCl) dissolved in a solvent (water). Is there any equation I can use to find this? I cannot use concentration, but I have the total mass of the solution, the total volume of the solution, and the molar mass of the solute (NaCl). I can also calculate the total density of the solution, so let's add that, as well.

    2. Relevant equations
    For the solute:
    Mass = Molarity x Molar Mass x Volume

    3. The attempt at a solution
    Using the equation above, I've tried to plug in different variables in the place of variables I didn't know up-front.

    Mass = Molarity x Molar Mass x Volume
    Mass = (Moles / Volume) x Molar Mass x Volume
    Mass = ((Mass / Molar Mass) / Volume) x Molar Mass x Volume
    Mass = ((Mass / Molar Mass) / (Mass / Density)) x Molar Mass x (Mass / Density)

    Of course, simplifying all of this cancels Mass, what I was trying to find in the first place, which makes me wonder why I even did all of that substitution for nothing.

    I'm thinking there's a different, better way to do this, probably a different equation. But, also, because I am doing this within an experiment, any hands-on method would work, too (just something feasible, please?).

    Thanks in advance!!!
  2. jcsd
  3. Nov 4, 2009 #2


    User Avatar

    Staff: Mentor

    Basically you can't do anything without knowing more. You can use density tables to check out concentration.

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