Density and Molar Volume
Ideal Gas Molar Volume at STP

Ideal Gas Molar Volume: The volume occupied by a mole of ideal gas at 0 C. This value is important: 22.7 L/mol
 Different gas molecules have different masses. Therefore, different gases must have different densities!
 $ d = \frac{mass}{volume} $
 STP density of $ N_2: d_{N_2} = \frac{28.02g/mol}{22.7L/mol} = 1.23g/L$
Denisty at any temperature and pressure

$PV = nRT –> (\frac{P}{RT}) == \frac{n}{V}$

$ d = \frac{PM}{RT} $
Molar Mass of an Unknown Gas

Suppose we have a volume of gas that might be any one of the Noble gases. Given V = 0.500 L at P = 700 Torr and T = 22.6 C has a mass of 1.6g
 Find the number of moles:
 $ n = \frac{700Torr*0.500L}{62.3635L Torr/K mol * (22.6+273.15)} = 1.89x10^2 $
 Molar mass is: $M = \frac{mass of sample}{moles in sample}$
 $M = \frac{1.6g}{1.89x10^2 moles} = 84.32g/mol$