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Topic: Calculating final pressure for sublimation  (Read 4371 times)

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Offline odicon

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Calculating final pressure for sublimation
« on: February 01, 2010, 04:02:52 PM »
The entropy of sublimation of a certain compound is 30.8 J / K mol at its normal sublimation point of 75 C. Calculate the vapour pressure in torr of the compound at 40 C. Assume that the enthalpy of sublimation is constant.
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The answer is 502 torr but I am not sure why. I got 1150 torr for some reason.
I used the following equations to get P(final):

Delta S = Delta H / T

ln(P(final)/P(initial) = Delta H / R * (1/T(final) - 1/T(initial))


I also used the following information: R = 8.314 J/Kmol
1atm = 760 Torr

I would really appreciate it if you could tell me what I am doing wrong.

Thank you very much.

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