R Value

[Laine Phillips]

In the equation W=-nRT ln Vf/Vi which value of R should we use or does it not matter?

[Steven Tjandra 1B]

Hello!

Honestly I also struggle with this. The difference between the 8.314 and the 0.0821 is that the first is J/(K·mol) while the second is (L·atm)/(K·mol). So the numerators are different. So you use the first one for equations where you're calculating energy and stuff like the equation you use, and the second when you're using the PV=nRT formula where you're calculating volume or pressure. So in this case you should use 8.314, unless you'll have the change up the terms you're using pretty significantly to match the units of the second form. (though technically the two gas constants are equal) So when I'm stuck I just write out all the units and see whether or not they cancel out to the form I'm interested in, in this case J for work.

Inconsistent,
Steven Tjandra

[Makayla Kubo 3A]

just check which units you're using to determine which of the two values has the units needed to cancel out the ones in your equation!

[Makayla Kubo 3A]

It all depends on how units cancel out, so even though it can be tedious, try to keep track of the different units as you cancel them out throughout the process of filling in the equaiton