The lowest pressure attainable using the best available techniques is about 10^-12 N/m^2. At such pressure, how many molecules are there per cm^3 at 0 degrees C.
I know that PV= nRT and that you solve for n/v = P/RT. I have also converted from N/m^2 to atm and am using R = .0821 atm L/ mole K and T = 273 K. How do you get the units to work out so cm^3 is on the bottom and after that how do you go from moles to molecules?