## Question 8.31

Marco_Romo_1M
Posts: 36
Joined: Wed Sep 21, 2016 2:59 pm

### Question 8.31

Are we supposed to know that the molar heat capacity of a monatomic ideal gas at constant pressure is 5/2 R? And at constant volume is 3/2 R? Where do these numbers come from?

Danny Nguyen 2H
Posts: 17
Joined: Fri Jul 22, 2016 3:00 am

### Re: Question 8.31

Hey, Marco interesting question. I looked more into it and in the textbook itself Section 8.10 pg 280-281 it gives the whole explantion on why for constant volume its (3/2)R and for constant pressure its (5/2)R. Hope that helped! and yes I assuming we should know these numbers.

Sarah_Heesacker_3B
Posts: 21
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Question 8.31

These values are given on the equation sheet on the back of the periodic table we received with the course reader. I think this means that they will likely be given to us on any tests or quizzes, so I don't think we need to memorize them.

Emi Nakahara 3F
Posts: 21
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Question 8.31

I've looked at the corresponding section in the textbook explaining why CP,m=(5/2)R, but I'm still lost on how to obtain the value 20.8 J per mols per degrees C that was in the solutions manual for question 31 from that equation.

Chem_Mod
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Joined: Thu Aug 04, 2011 1:53 pm
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### Re: Question 8.31

Use the value 8.3145 J/mol•K for R (this is different by a conversion factor from 0.08206 L•atm/mol•K)