Enthalpy of sublimation?

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Ryan Narisma 4G
Posts: 104
Joined: Fri Aug 30, 2019 12:18 am

Enthalpy of sublimation?

Postby Ryan Narisma 4G » Mon Jan 27, 2020 8:43 pm

Will we ever need to calculate the enthalpy of sublimation or use this value in any of our calculations? If so, how do you perform calculations using enthalpy of sublimation? Thank you!

505306205
Posts: 97
Joined: Thu Jul 25, 2019 12:15 am

Re: Enthalpy of sublimation?

Postby 505306205 » Mon Jan 27, 2020 8:46 pm

The enthalpy of sublimation is simply the sum of the heat of fusion and the heat of vaporization.

Jack Riley 4f
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Joined: Sat Aug 24, 2019 12:17 am

Re: Enthalpy of sublimation?

Postby Jack Riley 4f » Mon Jan 27, 2020 8:48 pm

the enthalpy of sublimation is the sum of the enthalpy of vaporization and fusion

Harry Zhang 1B
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Joined: Sat Sep 14, 2019 12:16 am

Re: Enthalpy of sublimation?

Postby Harry Zhang 1B » Mon Jan 27, 2020 9:34 pm

Since enthalpy is a state function and sublimation means the subject goes from a solid to a gas, the enthalpy of sublimation=heat involved in fusion+heat involved in vaporization

Uisa_Manumaleuna_3E
Posts: 60
Joined: Wed Sep 21, 2016 2:56 pm

Re: Enthalpy of sublimation?

Postby Uisa_Manumaleuna_3E » Thu Jan 30, 2020 7:45 pm

Understanding that you calculate the enthalpy of sublimation with the enthalpy of fusion and of vaporization lets you understand that enthalpy is additive, a state property. So for our purposes, it is helpful in that sense.

However, you'll probably see that we don't actually calculate the enthalpy of sublimation all too often, at least not immediately in the HW problems. Understanding the calculation of sublimation energy is kind of that real world application that you would actually study more of in a lab.

705367472
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Joined: Tue Nov 19, 2019 12:19 am

Re: Enthalpy of sublimation?

Postby 705367472 » Thu Jan 30, 2020 10:27 pm

Ethalpy of sublimation is positive because it requires heat and therefore it would be endothermic. Also it is important to remember that phase changes are constant T.

Shutong Hou_1F
Posts: 117
Joined: Sat Sep 14, 2019 12:17 am

Re: Enthalpy of sublimation?

Postby Shutong Hou_1F » Fri Jan 31, 2020 9:46 pm

Vaporization, melting (fusion), and sublimation are all exothermic reactions, so the change of enthralpy of each of these three reactions has a positive value.
delta H(vap) = H(vapor) - H(liquid);
delta H(fus) = H(liquid) - H(solid);
delta H(sub) = H(vapor) - H(solid);
So delta H(sub) = delta H(fus) + delta H(vap).

Orrin Zhong 4G
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Joined: Sat Jul 20, 2019 12:16 am

Re: Enthalpy of sublimation?

Postby Orrin Zhong 4G » Fri Jan 31, 2020 9:54 pm

Sublimation is the phase change from a solid directly to a liquid. Therefore, the enthalpy of sublimation is the change in enthalpy from a solid to a gas. The enthalpy of sublimation is the sum of the enthalpy of fusion and the enthalpy of vaporization: ΔH(sublimation) = ΔH(vaporization) + ΔH(fusion) = (H(gas) - H(liquid)) + (H(liquid) - H(solid)) = H(gas) - H(solid).

HuyHa_2H
Posts: 100
Joined: Wed Sep 11, 2019 12:15 am

Re: Enthalpy of sublimation?

Postby HuyHa_2H » Sat Feb 01, 2020 2:35 am

We will eventually have to calculate the enthalpy of sublimation and is represented by the sum of the heat of fusion and the heat of vaporization.


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