ideal gas constant


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josephyim1L
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

ideal gas constant

Postby josephyim1L » Wed Jan 09, 2019 5:18 pm

what is the R value for PV=nRT that we are using in order to solve for partial pressure or concentration (n/V) ?

Manya Bali 4E
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

Re: ideal gas constant

Postby Manya Bali 4E » Wed Jan 09, 2019 5:35 pm

On the 14B website, there's a link to a Constants and Equations PDF that essentially has everything we would need to know for the class. From there, you can see that the R value (Gas constant) is 8.314 J·K^-1·mol^-1 or 8.206 x 10^2 L·atm·K^-1·mol^-1 or 8.314 x 10^2 L·bar·K^-1·mol^-1 or 62.364 L·Torr·K^-1·mol^-1.

Greta Mascareno 1B
Posts: 2
Joined: Wed Nov 14, 2018 12:23 am

Re: ideal gas constant

Postby Greta Mascareno 1B » Wed Jan 09, 2019 5:55 pm

Also, there is an example (51.3 on pg.419) in the seventh edition of the textbook that uses 8.3145*10^-2 L*bar*K^-1*mol^-1 as R to find the partial pressure of the reactant. They use moles, liters, and kelvin for the other units.

hazelyang2E
Posts: 57
Joined: Fri Sep 28, 2018 12:23 am

Re: ideal gas constant

Postby hazelyang2E » Wed Jan 09, 2019 6:28 pm

I believe one of the most commonly used values for the R constant is 8.206 x 10-2 L·atm/K·mol, but it is important to keep in mind that this value can change depending on which units are being used as shown in the previous answers. Also, my TA mentioned that this constant will be provided for us on exams so we do not need to memorize it, but that we should know the most commonly used unit conversions (i.e. mL to L, bar to atm, etc.) in order to make sure that all of the units cancel out in the end.

Eric Quach 1C
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: ideal gas constant

Postby Eric Quach 1C » Wed Jan 09, 2019 7:41 pm

The value of R used is dependent upon the unit of pressure used.
For example if atmosphere is the unit of pressure used then 0.08206 is the R value. However, if torr is the unit of pressure used then use the R value of 62.36.


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