Calculating the heat of vaporization of chloroform [thermochemistry]

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SUMMARY

The discussion focuses on calculating the heat of vaporization (ΔHvapor) of chloroform (TCM) using the Clausius-Clapeyron relation. Participants are tasked with plotting vapor pressure (Pvapor) against temperature (T) and lnPvapor against 1/T to derive ΔHvapor. The key challenge is determining the boiling point by extrapolating the vapor pressure data to find the temperature at which Pvapor equals the barometric pressure. Additionally, the constant C, related to the entropy of vaporization, is assumed to be independent of temperature and pressure.

PREREQUISITES
  • Understanding of the Clausius-Clapeyron relation
  • Familiarity with plotting and interpreting vapor pressure data
  • Knowledge of thermodynamic concepts such as heat of vaporization
  • Basic skills in data extrapolation techniques
NEXT STEPS
  • Learn how to plot vapor pressure data and determine boiling points from experimental data
  • Study the derivation and application of the Clausius-Clapeyron equation
  • Research methods for calculating ΔHvapor from experimental vapor pressure data
  • Explore the significance of the constant C in thermodynamic equations
USEFUL FOR

Chemistry students, laboratory researchers, and anyone involved in thermochemical analysis or vapor pressure studies will benefit from this discussion.

anisotropic
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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:
Chemistry news on Phys.org
Extrapolation OK, assume C is just a constant and not a function neither of P nor T.
 

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