What exactly is 3/2RT and when do we use it?

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Kobe_Wright
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Joined: Fri Sep 28, 2018 12:16 am

What exactly is 3/2RT and when do we use it?

Postby Kobe_Wright » Wed Feb 06, 2019 3:11 pm

Title

Ava Kjos 1D
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Joined: Fri Sep 28, 2018 12:19 am

Re: What exactly is 3/2RT and when do we use it?

Postby Ava Kjos 1D » Wed Feb 06, 2019 4:03 pm

Internal energy is energy stored as kinetic energy and potential energy that can move in different ways, including translational energy, rotational energy, and vibrational energy. The translational energy is equivalent to 3/2RT and the rotational energy of a nonlinear molecule is also 3/2RT. Both of these contribute these help to determine the change in internal energy.

The textbook goes into more depth on this. I'm not sure where in the 6th edition it is, but if you have the 7th edition you can read 4B.3 (pages 260-261) for a better explanation.

Matthew Mar 1J
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Re: What exactly is 3/2RT and when do we use it?

Postby Matthew Mar 1J » Sat Feb 09, 2019 5:59 pm

I don't know if this is directly related, but 3/2R (without the T) is the specific heat capacity of a monatomic ideal gas at constant volume (Cv) which is used in entropy problems (/\S = n Cv ln(T1/T2)) which is a more practical application.

Kobe_Wright
Posts: 83
Joined: Fri Sep 28, 2018 12:16 am

Re: What exactly is 3/2RT and when do we use it?

Postby Kobe_Wright » Sat Feb 09, 2019 7:11 pm

Matthew Mar 1J wrote:I don't know if this is directly related, but 3/2R (without the T) is the specific heat capacity of a monatomic ideal gas at constant volume (Cv) which is used in entropy problems (/\S = n Cv ln(T1/T2)) which is a more practical application.

Then what about when it is constant pressure?

Abby-Hile-1F
Posts: 46
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Re: What exactly is 3/2RT and when do we use it?

Postby Abby-Hile-1F » Sun Feb 10, 2019 4:39 pm

Do you just use 5/2R when it is at constant pressure?


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