Cv and Cp

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Parker Smith
Posts: 102
Joined: Thu Jul 25, 2019 12:15 am

Cv and Cp

Postby Parker Smith » Tue Jan 28, 2020 2:04 pm

Dr. Lavelle said that Cp is equivalent to enthalpy change, but why is Cv not included in this?

Kevin Xu 4F
Posts: 50
Joined: Fri Aug 09, 2019 12:16 am

Re: Cv and Cp

Postby Kevin Xu 4F » Tue Jan 28, 2020 2:15 pm

I think both Cv and Cp can be used to calculator enthalpy change in the formula q= nCT. Just know that Cv means the molar heat capacity of a gas at a constant volume whereas Cp means the molar heat capacity of a gas at a constant pressure.

WesleyWu_1C
Posts: 117
Joined: Thu Jul 25, 2019 12:16 am

Re: Cv and Cp

Postby WesleyWu_1C » Tue Jan 28, 2020 6:00 pm

Since enthalpy change is usually under constant pressure, maybe that's why only Cp equals enthalpy change.

Leila_4G
Posts: 114
Joined: Sat Sep 14, 2019 12:17 am

Re: Cv and Cp

Postby Leila_4G » Tue Jan 28, 2020 7:55 pm

Do solids and liquids only use C? Or do they use Cv? I'm pretty sure they don't use Cp.

Luc Zelissen 1K
Posts: 57
Joined: Mon Jun 17, 2019 7:23 am

Re: Cv and Cp

Postby Luc Zelissen 1K » Tue Jan 28, 2020 7:57 pm

Leila_4E wrote:Do solids and liquids only use C? Or do they use Cv? I'm pretty sure they don't use Cp.

They are the same for solids and liquids. For gasses, they are easily compressible, meaning their specific volume can easily change, while solids and liquids cannot change volume that easily so we just say that Cv=Cp.

Emily Chirila 2E
Posts: 112
Joined: Sat Jul 20, 2019 12:16 am

Re: Cv and Cp

Postby Emily Chirila 2E » Tue Jan 28, 2020 8:48 pm

The values are the same in solids and liquids. In gases, Cv is constant volume and Cp is constant pressure so the values will be different. I think Cp may be used because Cp calorimetry gives enthalpy values, whereas Cv calorimetry gives heat capacity of the whole container/all parts

ValerieChavarin 4F
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Joined: Wed Sep 18, 2019 12:18 am

Re: Cv and Cp

Postby ValerieChavarin 4F » Thu Jan 30, 2020 4:08 pm

They are equal in the case of solids and liquids but change for gases due to compression and expansion.

705367472
Posts: 22
Joined: Tue Nov 19, 2019 12:19 am

Re: Cv and Cp

Postby 705367472 » Thu Jan 30, 2020 10:17 pm

So solids and liquids only use C? Also for gases it depends on certain factors?

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

Re: Cv and Cp

Postby Shutong Hou_1F » Fri Jan 31, 2020 10:07 pm

The change in enthalpy is equal to heat released or absorbed only when the reaction happens at a constant pressure. So the value of q(heat) calculated by Cp is equal to change in enthalpy, but not by Cv.

AniP_2D
Posts: 95
Joined: Sat Aug 17, 2019 12:17 am

Re: Cv and Cp

Postby AniP_2D » Sun Feb 02, 2020 1:58 pm

If I'm not mistaken, Cv is used under constant volume while Cp is used under constant pressure.


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