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Homework Help: Freezing point estimation

  1. Jun 26, 2005 #1
    ethanol 46g/mol freezes at 3.65degC density changes from 0.789g/cm-3 to 0.801g/cm-3 latent hear of fusion 8.68kJ/mol. freezing point at 1000 atm.

    i calculated the ansfer from an example and just want to verify if its correct.

    dp/dt=(dfusH)/(t*dfusV) rearanged to dt=(dp*t*dfusV)/dfusH
    where dfusV: change in molar volume on melting

    okay, with the rearanged equation i changed 1000 atm to pascals = 101325 kPa dfusV was calculated to be 4.875399e-6 m3/mol
    i came to a change in temperature of 15.54deg hence final freezing point is 11.8956degC.

    could anyone plese help me and tell me if this is correct
    also.. in teh equation t=273.15K was used.. could anyone please tell me why this was the case?
    thanks
    patrick.
     
  2. jcsd
  3. Jun 28, 2005 #2
    I don't know the freezing point, but you can probably find a table that gives you that data so you can check your answers.

    Also, you use t = 273.15 Kelvins because that is, in basic terms, the accepted unit of temperature in chemistry/physics, etc. You will use Kelvins in the gas laws, thermochemistry and thermophysics, and pretty much everything else.
     
    Last edited by a moderator: Jun 29, 2005
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