Experimental evidences show that one mole of all gases under similar conditions of temperature and pressure occupy the same volume called molar volume (Vm). Molar volume of all gases under normal pressures (1 atm) and normal temperature (273K) have a value of 22.4 litre and contains 6.023 x 1023molecules. The number is called the Avogadro's number or Avogadro's constant and is denoted by NA.Avogadro's law has been useful in substantiating a number of important laws and concepts. It has helped in the following areas:
- In explaining Gay Lussac's law of gaseous volumes.
- In determining the atomicity of gases.
- In determining the molecular formula of a gas.
- In establishing the relationship between relative molecular mass and vapour density.