The problem statement, all variables and given/known data Argon (atomic weight 40) exists as a monatomic gas at room temperature and pressure. The density of liquid argon is 1784 kg m−3. (a) Calculate the atomic density (atoms m−3) in liquid argon. (b) Calculate the atomic density (atoms m−3) in gaseous argon at a pressure of 1 atm and a temperature of 300K. The attempt at a solution (a) PV = NkT where, P = 1.01 x 105 k = 1.38 x 10-23 T = 300 N/V = P/kT = 2.44 x 1025 atoms m−3 (b) I have no idea. I know there should be a difference but I don't know what to do. I think perhaps my answer to (a) is in fact the answer to (b) in which case, how do I answer (a)?