Avogadro's Hypothesis

↪ This law states, "Under similar conditions of pressure and temperature, equal volume of all the gaseous substance contain equal number of molecules."

Mathematically,

Volume(v) ∝ No. of Molecules (n) {under similar condition of pressure and temperature}

22.4l of Hydrogen at NTP = 6.023x10²³ No. of molecules of H₂ = 2g
22.4l of Nitrogen at NTP = 6.023x10²³ No. of molecules of N₂ = 28g
22.4l of CO₂ at NTP = 6.023x10²³ No. of molecules of CO₂ = 44g
22.4l of O at NTP = 6.023x10²³ No. of molecules of O₂ = 32g
22.4l of CO at NTP = 6.023x10²³ No. of molecules of CO = 28g

⁕ 1 mole or mol :

↪ It is the collection of 6.023x10²³ No. of chemical species. (atoms, ions, compounds, molecules or electrons)

For examples,

1 mole of Na = 6.023x10²³ No. of Na atoms
1 mole of Ca = 6.023x10²³ No. of Ca atoms
1 mole of K = 6.023x10²³ No. of K atoms
1 mole of CO₂ = 6.023x10²³ No. of CO₂ 
1 mole of Nitrogen gas = 6.023x10²³ No. of N₂ gas
1 mole of Na⁺ = 6.023x10²³ No. of Na ions
1 mole of H⁺ = 6.023x10²³ No. of H ions
1 mole of e^- = 6.023x10²³ No. of electrons