enthalpy of phase changes

[205389184]

Will a calculation of the enthalpy of vaporization, fusion, or sublimation ever result in a negative value?

[Aliya Jain 2B]

I dont think so, because heat is always required during those phase changes

[KSong_1J]

The textbook states that enthalpies of fusion and vaporization are always positive and I’m pretty sure the same goes for the enthalpy of sublimation (since it’s the conversion of a solid to vapor so it’s endothermic)

[405268063]

I would think that since heat is required to make those phase changes, the reaction would be endothermic. Therefore, delta H would have to be positive.

[RasikaObla_4I]

No because it requires heat energy to go from a solid to a liquid to vapor so the reactions would be endothermic.

[605395381]

I do not believe that enthalpy values will ever be negative

[Eesha Chattopadhyay 2K]

No, calculating the enthalpy of a phase change will not be negative.

[DHavo_1E]

Hello,

In response to this question, could anyone explain why the bond enthalpies in Dr. Lavelle's example were positive AND negative?

[AGaeta_2C]

Hello,

In response to this question, could anyone explain why the bond enthalpies in Dr. Lavelle's example were positive AND negative?

Bond energy can be described as the energy it takes to break a bond, in this case, the values would be positive.
Therefore, the energy it takes to form bonds would be negative.