posted by Peter .
Is there an easy way to re-write PV=nRT so that it equates density with molar mass?
Yes. I'll show you how to do it. I never remember the formula but I know how to get it if I need it.
PV = nRT
n = moles = grams/molar mass; substitute.
PV = (g/M)RT where M is molar mass.
Rearrange to PVM = gRT.
Density = g/v (in liters).
PM = (g/V)RT
PM = dRT where d is density. You must remember density is in g/L and not g/mL as is so often quoted.