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Homework Help: Enthalpy of vaporization of hexane

  1. Jun 8, 2014 #1
    1. The problem statement, all variables and given/known data
    The normal boiling point of hexane is 69.0°C. Estimate (a) its enthalpy
    of vaporization

    3. The attempt at a solution
    In order to solve for ΔHvap in the Clausius-Clapeyron equation I need a reference T and p point. I extracted it from the triple point (T=178K and p=1,23Pa).
    I solve and I get 34kJ/mol, while the answer is 29,1kJ/mol. What i've done wrong?

  2. jcsd
  3. Jun 8, 2014 #2


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    Science Advisor
    Gold Member

    The Clausius-Clapeyron equation is just an approximation, because it is assumed in deriving it that the enthalpy of vaporization is temperature independent and that the gas phase behaves as an ideal gas. Like it's said in the question, you are only expected to give an estimate, anyway.
  4. Jun 8, 2014 #3
    So how would you do to get a more accurate result? One option is to get a (T,p) point closer to the desired 69ºC and 1bar, but if this is not available...?
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