Phase Changes

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donnanguyen1d
Posts: 64
Joined: Fri Sep 29, 2017 7:04 am

Phase Changes

Postby donnanguyen1d » Wed Jan 10, 2018 9:46 pm

The enthalpy of sublimation of a substance must be = to the sum of the enthalpies of fusion and vaporization, "provided that they are measured at the same temperature". Regarding the temperature part of this statement, does that mean all enthalpies are at the same temperature? or what's the temperature's role?

skalvakota2H
Posts: 52
Joined: Sat Jul 22, 2017 3:01 am

Re: Phase Changes

Postby skalvakota2H » Wed Jan 10, 2018 9:54 pm

Yes, given that the enthalpies are organized into a table, this means that these values must be given at a specific temperature. Hence, we can assume that the reactions will be paired with enthalpies at 25 degrees Celsius.

Lisa Tang 1C
Posts: 62
Joined: Fri Sep 29, 2017 7:05 am
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Re: Phase Changes

Postby Lisa Tang 1C » Wed Jan 10, 2018 9:58 pm

The temperature part refers to the fact that the enthalpy of sublimation of a substance can only equal the sum of the enthalpies of fusion and vaporization when these two values are measured at the same temperature. Temperature is important to take into account because substances tend to have different enthalpies at different temperatures.


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