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Calculating the heat of vaporization of chloroform [thermochemistry]

  1. Feb 13, 2009 #1
    I am doing a lab writeup and am completely lost.

    Summary of lab itself:
    • Calculated the vapour pressure of chloroform (TCM) across a range of temperatures (using flask apparatus).
    • Objective is to determine the heat of vaporization of TCM using the variation of vapour pressure with temperature.

    Other info we are provided:
    • Provided the Clausius-Clapeyron relation (lnP = -ΔHv/RT + C)
    • "is independent of temperature"
    • "C is a constant related to the entropy of vaporization"

    I'm supposed to:
    • plot Pvapor vs. T, and determine the boiling temp.
    • plot lnPvapor vs. 1/T, and determine ΔHvapor

    My questions:
    • How do you calculate boiling point from this data? I am assuming it involves extrapolating and determining at what temperature Pvapor = Pbarometric ?
    • How do you calculate ΔHvapor from this data without knowing C? That is, how are lnPvapor and 1/T related to C? (we are not given C and are supposed to determine it from the data)

    Help would be appreciated.
    Last edited: Feb 13, 2009
  2. jcsd
  3. Feb 13, 2009 #2


    User Avatar

    Staff: Mentor

    Extrapolation OK, assume C is just a constant and not a function neither of P nor T.
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