Different R values

[Maya F 1E]

How do you determine which value of R to use while calculating with gas? (8.314 vs 0.0821)

[George_Furey_1C]

You have to look at the units of the data you're working with. 8.314 is measured in J/K*mol whereas 0.0821 is measured in L*atm/K*mol. Basically you need your units to cancel out so you use the corresponding R value to do that.

[Valeria Perez 3J]

In theory, you should be able to use them interchangeably, but if you choose one that doesn't quite match your units, you may need to do some converting in order to achieve the correct results. Therefore, like the person above stated, its best to use the ones that matches your units most closely, so that you limit the amount of conversions you need to do and make your calculations easier.

[Jacob Fossa 3A]

Hi, I think an example of the units being cancelled might clear things up for you. In syllabus problem 4A.5 b) we set up the equation for work: w = -nRTln(V2/V1). Because n is .2 mol, T is 298 K, and we want our answer in J, we use R as 8.314 J/mol K so that mol and Kelvin will cancel out, leaving only Joules.