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Molality to mass

  1. Apr 7, 2010 #1
    1. The problem statement, all variables and given/known data
    Hi. This is a question based on a lab I did.

    We mixed an unknown solute in a solution of pure cyclohexane. Based on numbers we got from our lab, we were asked to find the molal concentration of the unknown. The freezing point of the unkown was found to be 1.5 C and the freezing point of the cyclohexane was found to be 6.7 C. Therefore Delta Tf is 5.2 C. the Kf of the cyclohexane was found to be 12.5 C/molality.

    so i found the molality of the unkown to be .416 mol/kg

    we are asked now to find the mass of the unkown that would dissolve in 1kg of cyclohexane to give the same molal concentration that we had in our solution.

    i'm not seeing how the heck i can find mass from this the information I have.

    We will lastly have to find the molar mass of the unkown. I can't find this until i have figured out the mass of the unkown

    any help would be appreciated! thank you

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 8, 2010 #2


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    Staff: Mentor

    Please describe precisely the experiment as it was done and all information you were given. I agree that at present there is not enough data, but could be you are ignoring some crucial information not seeing how it is related to the question.

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