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Homework Help: Fractional Distillation Calculations

  1. Mar 21, 2012 #1
    1. The problem statement, all variables and given/known data

    4-bromotoluene was synthesized and purified by distillation. There are 5ml of the crude product. A fractional distillation is being carried out in a 100ml round bottom flask. Assume that the volume of the column is 16ml. Determine the number of moles of 4-bromotoluene that will remain vaporized and cannot be collected. What will the volume of the condensed vapor be?

    2. Relevant equations

    Total Pressure=χaPa+χbPb, where χis the mole fraction of a or b and P is the normal pressure of a or b.
    bp of 4-bromotoluene is 184C

    3. The attempt at a solution

    I know that we are trying to find n using PV=nRT. However, I'm not sure which values we plug in. Do I use V=16ml for the volume inside the column? Do I use the boiling point for T? Also, how do you find the pressure of the system? If P= the total pressure of the mixture, how would you find it if you don't know how much of the compound is made up of 4-bromotoluene and what the pressure of 4-bromotoluene is?

    Thank you very much!
  2. jcsd
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