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Homework Help: Determining boiling point from vapour pressure

  1. Oct 26, 2015 #1
    1. The problem statement, all variables and given/known data
    When benzene freezes at 5.5 C its density changes from 0.879 g cm-3 to 0.891 g cm-3. Its enthalpy of fusion is 10.59 kJ mol -1. Estimate freezing point of benzene at 1000 atm
    2. Relevant equations
    Solid liquid boundary: p=p*+ΔHfus/ΔV ln(T/T*)

    3. The attempt at a solution
    From the equation I can solve for T which I do not have a problem with. For ΔV fus I thought to take the the difference of the densities and then using the molar mass of benzene, 78.1 g/mol, get ΔVm in cm-3.This is then converted to m-3. I made the assumption that the first part is occurring under normal conditions, so 1 atm for the freezing point at 5.5 C given in the problem. I think assuming 1 atm is my biggest mistake when solving this problem because I think that everything else is just plugging in the values.
  2. jcsd
  3. Oct 26, 2015 #2


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    2017 Award

    Staff: Mentor

    The 5.5 C probably refer to atmospheric pressure, but it doesn't change much to assume other low pressures.

    ΔV in cm-3 doesn't have correct units. You need volume per mole to make the units match.
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