Gases ❮ 121● Graham’s law—The lower the molecular mass of a gas, the faster it will effuse/diffuse.
Know how to use Graham’s law: M
M
=
r
r1
22
1.
● Gas stoichiometry—Know how to apply the gas laws to reaction stoichiometry
problems.
● Non-ideal gases—Know how the van der Waals equation accounts for the non-ideal
behavior of real gases.
● Tips—Make sure the temperature is in Kelvin; gas laws are being applied to gases only;
the units cancel; and the answer is reasonable.
● Gas laws are very useful for gases, but not for liquids and solids. Before applying a gas
law, be sure you are dealing with a gas.