A tank of compressed air of volume 1.0 m^3 is pressurized to 50 atm at T = 273 K. A valve is opened and air is released until the pressure in the tank is 17 atm. How many air molecules were released? I tried this problem using PV = NkT and PV = nRT. I realize the difference in these equations and I was wondering if this in fact the right equations to use? I ran 50 atm through and then 17 atm through. I then subtracted the initial N minus the final N. This didn't work. This is what I did: (50 atm)(1.0 m^3) = N(1.38e-23)(273) N = 1.327e22 (17)(1.0 m^3) = N(1.38e-23)(273) N = 4.512e21 Nfinal = (1.327e22) - (4.512e21) Nfinal = 8.758e21 This is the wrong answer. What should I do?