Avogadro's Law
Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.
Formula / equation
V ∝ n
Unit
L/mol
In depth
Because gas molecules are so far apart, the volume depends on how many particles are present rather than on what they are. The law resolved the confusion between atoms and molecules in early chemistry and gives the molar volume of 22.4 L/mol at STP for every gas.
Examples in the real world
One litre of hydrogen and one litre of carbon dioxide at the same conditions contain the same number of molecules.