Boiling Point Mystery for Ethyl Alcohol

AI Thread Summary
The discussion revolves around determining the temperature at which the vapor pressure of ethyl alcohol reaches 357 mm Hg, given its normal boiling point and entropy. The original poster expresses confusion about the relationship between pressure, entropy, and phase transitions, considering the Gibbs free energy and equilibrium concepts. Participants suggest using the Clapeyron equation, which relates the change in pressure during a phase transition to temperature and enthalpy changes, which are in turn linked to entropy changes. The poster intends to share their calculations later, indicating ongoing engagement with the problem. Overall, the thread focuses on clarifying the application of thermodynamic principles to solve the boiling point mystery for ethyl alcohol.
rxrocky
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Hello everyone!

I've encountered a small problem with one of our "special" assignments.

Question:
The normal boiling point for ethyl alcohol is 78.4 C, S for C2H5OH(g) is 282,7 J/mol*K.
At what temperature is the vapor pressure of ethyl alcohol 357 mm Hg?

Maybe I'm stupid, but I can't find a connection between the pressure and entropy. Or the phase transition. Original I thought it had something to do with Gibbs vs equilibrium, but now I'm even more confused.

I'd love to do the problem myself but I'm in need of a hint/tip :)

Thanks in advance.
 
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The only equation that comes to mind at the moment is some type of derivative of the Clayperon equation.
 
Yes, this is definitely a Clapeyron relation problem. The change in characteristic pressure of a phase transformation with temperature is related to the enthalpy of the transformation. And the enthalpy change is related to the entropy change. Let us know if you get stuck.
 
Thanks for the help.

I'll post my calculations later today, still not entirley sure I got it right.
 
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