Gas constant, R

Volume:
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Aschreck 2G
Posts: 9
Joined: Fri Sep 25, 2015 3:00 am

Gas constant, R

Postby Aschreck 2G » Sun Feb 07, 2016 10:52 pm

How do you determine which value of R to use in calculations, 8.314 or .0821??

Malaya Du 2G
Posts: 8
Joined: Fri Sep 25, 2015 3:00 am

Re: Gas constant, R

Postby Malaya Du 2G » Sun Feb 07, 2016 10:58 pm

It depends on what units are needed for the problem. .082 is in L atm/ K mol while 8.314 is in J/K mol. Usually we use 8.314 because we are dealing with Joules.

Daniel Fu 2K
Posts: 10
Joined: Fri Sep 25, 2015 3:00 am

Re: Gas constant, R

Postby Daniel Fu 2K » Sun Feb 07, 2016 11:04 pm

8.31 J K^−1 mol^−1 is used when you have the gas quantity in moles, pressure in N/m^2, T in ºK and volume in m^3

0.0821 L atm K^−1 mol^−1is used when you have the gas quantity in moles, the volume in L, pressure in atm and T in ºK

But in case you forget, just make sure you know the units associated with the numbers and just try and use the one that makes the unit cancellation work out.


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