3/2 and 5/2 R

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Brooke VanSickle 1J
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3/2 and 5/2 R

Postby Brooke VanSickle 1J » Sun Jan 17, 2016 9:02 pm

Can someone please explain when to use 3/2R and 5/2R in calculations?
Thanks!

Dan Dinh 3K
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Re: 3/2 and 5/2 R

Postby Dan Dinh 3K » Sun Jan 17, 2016 9:19 pm

If the ideal gas is at constant volume then you use 3/2R and if the ideal gas is at constant pressure then you use 5/2R.

004594950
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Re: 3/2 and 5/2 R

Postby 004594950 » Wed Jan 20, 2016 6:44 pm

Brooke VanSickle 1J wrote:Can someone please explain when to use 3/2R and 5/2R in calculations?
Thanks!


When the volume is constant, you use 3/2R.
When pressure is constant, you use 5/2R.

Chem_Mod
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Re: 3/2 and 5/2 R

Postby Chem_Mod » Wed Jan 20, 2016 11:03 pm

Please note that deltaU always uses 3/2 R. deltaU is the heat that would be transferred at constant volume, so you use Cv. It does not care whether your process is ACTUALLY at constant volume. dU = Cv*dT. Similarly, dH = Cp*dT since enthalpy is the heat that would be transferred at constant pressure.

Camryn Marshall 1C
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Re: 3/2 and 5/2 R

Postby Camryn Marshall 1C » Thu Jan 21, 2016 12:37 am

How would we have known this without seeing it in the solutions manual? Is it listed somewhere in the textbook?

Heerali Patel 3A
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Re: 3/2 and 5/2 R

Postby Heerali Patel 3A » Thu Jan 21, 2016 11:41 am

Camryn Marshall 1C wrote:How would we have known this without seeing it in the solutions manual? Is it listed somewhere in the textbook?


Yes! It is discussed in Section 8.10, specifically on page 281.


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