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### 3/2R vs 5/2R

Posted: Wed Feb 13, 2019 12:05 am
how can we tell when to use 3/2R and 5/2R as C?

### Re: 3/2R vs 5/2R

Posted: Wed Feb 13, 2019 12:30 am
3/2R is used when it is at constant volume for a monoatomic ideal gas
5/2R is used when it is at constant pressure for a monoatomic ideal gas

### Re: 3/2R vs 5/2R

Posted: Thu Feb 14, 2019 5:08 pm
Agreed. You know which one to use in the context of the problem, so it's important to identify what is being held constant in the given problem

### Re: 3/2R vs 5/2R

Posted: Thu Feb 14, 2019 8:39 pm
It is very important to know the difference between. 5/2R is used for constant pressure and 3/2R is used for constant volume. You will have to use either one depending on the context of the question.

### Re: 3/2R vs 5/2R

Posted: Thu Feb 14, 2019 9:26 pm
Is (3/2 R) the same as Cn when you are trying the change in entropy when there is a temperature difference?

### Re: 3/2R vs 5/2R

Posted: Fri Feb 15, 2019 2:05 pm
When it is constant pressure or constant volume. Or based on the shape of the molecules.

### Re: 3/2R vs 5/2R

Posted: Fri Feb 15, 2019 2:39 pm
3/2 R is used for Cv of an ideal monoatomic atom. 5/2R is for Cv of a linear molecule and for Cp of an ideal monoatomic atom.

### Re: 3/2R vs 5/2R

Posted: Sat Feb 16, 2019 9:06 pm
3/2 R is used for a monoatomic ideal gas at constant volume where 5/2 R is used is used for a monoatomic gas at constant pressure, or for a linear molecule at constant volume.

### Re: 3/2R vs 5/2R

Posted: Sat Feb 16, 2019 9:48 pm
In addition to the other answers, the heat capacity at constant volume and the heat capacity at constant temperature are always separated by a factor of R. (C)v,m = R + (C)p,m. So, for single atoms 3/2R is the (C)v,m and 5/2R is the (C)P,m, while linear atoms have a (C)v,m of 5/2R, and more complicated molecules have a (C)v,m of 3R.