Avogadro, in 1813, gave this law. It relates the volume and number of particles of ideal gases at constant temperature and pressure. It states
“Equal volumes of all gases at the same temperature and pressure contain the same number of molecules.”
It means if two gases have the same volume, same temperature and same pressure then their number of molecules will also be the same. Mathematically law can be written as :
V ∝ n
Or V = Kn
On the bases of this law, Avogadro pointed that
22.4 dm3 of any gas at STP contains 6.02 x 1023 molecules.
Or 24 dm3 of any gas at RTP contains 6.02 x 1023 molecules.
Or in other words
Volume of 6.02 x 1023 molecules of any gas at STP = 22.4 dm3
Volume of 6.02 x 1023 molecules of any gas at RTP = 24 dm3