So for those of you who clicked on this video, let's see how we derived this new version of the ideal gas law. So we start out with the molar mass formula. Remember, molar mass equals mass M divided by moles N. Here we're going to algebraically rearrange this formula to isolate N. So first you're going to multiply both sides by N. So now it becomes M times N equals lowercase m.

To isolate N and moles, we divide out molar mass. So we're going to say here moles equals mass divided by molar mass. Going to the ideal gas law formula, we can now substitute N for this value here. So PV equals NRT now becomes PV equals mass over molar mass. We need to isolate our molar mass.

So what I'm going to do here is I'm going to multiply both sides by molar mass. Here is a denominator so I can multiply to get rid of it, and that equals mass times RT. Finally, to isolate our molar mass, we divide both sides by PV, and that's how we got that molar mass equals MRT/PV.

Again, this is the way we derived it if your professor wants you to show the work. But again, it's always easier to remember that molar mass really tests our valuable patience. Remembering that will help you remember this version of the ideal gas law.