Avogadro’s law states:
At the same temperature and pressure, equal volumes of all gases contain the same number of molecules.
Key points:
- The type of gas doesn’t matter—hydrogen, oxygen, or nitrogen—all have the same number of molecules if volume, temperature, and pressure are equal.
- This means the volume of a gas is directly proportional to the number of moles (n) when temperature and pressure are constant.
Example:
- 1 mole of any gas at standard temperature and pressure (STP: 0 °C and 1 atm) occupies 22.4 liters.
- So, 2 moles of gas will occupy 44.8 liters at STP.
In simple words:
Equal volumes of gases, under the same conditions, hold equal numbers of molecules.