Avogadro's Law

The Fundamental Principle

"Equal volumes of all gases at the same temperature and pressure contain the same number of molecules."

This revolutionary idea, proposed by Amedeo Avogadro in 1811, resolved many inconsistencies in chemistry and led to our modern understanding of molecules.

Mathematical Expression

Avogadro's Law can be expressed as:

V1n1=V2n2\frac{V_1}{n_1} = \frac{V_2}{n_2}

where:

  • V = volume of gas
  • n = number of moles
  • Temperature (T) and Pressure (P) remain constant

Implications

Avogadro's Law helped establish that:

  • Elements could exist as diatomic molecules (e.g., H₂, O₂)
  • The volume of a gas is directly proportional to the number of moles
  • One mole of any gas occupies the same volume at given temperature and pressure

Avogadro's Number

The number of particles in one mole of any substance:

NA=6.022×1023 particles/moleN_A = 6.022 \times 10^{23} \text{ particles/mole}