Avogadro's Law

Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto (1776-1856), also known as Amedeo Avogadro, was an Italian chemist who is most famous for his contribution with the molecular theory, which is now known as Avogadro's Law.

Amedeo was born in Turin, Italy into a family of well established lawyers.  He also followed into the footsteps of his family and got a bachelor of jurisprudence in 1792.  In 1796, just four year later, Amedeo received his doctorate of ecclesiastical law and soon began his practice.  However, after approximately 5 years Amedeo began to take an interest in mathematics and physics (back then it was known as philosophy).  In 1809 he started teaching at a high school and this is where he declared his hypothesis of Avogadro's Law.  It wasn't until 1858 that Avogadro's Law was accepted, when another chemist named Stanislao Cannizzaro was able to explain the organic exceptions of the law.

Avogadro's Law states that at a constant temperature and pressure, equal volumes of gases contain equal amounts of molecules.  If the amount of gas in a container is increased then the volume is increased.  According to this law,  V1/n1 = constant and after a change in the volume and mole number then V2/n2 = constant.  By combining these two equations we then get V1/n1 = V2/n2 which can be derived from the kinetic theory of gases under the assumption of an ideal gas.

Amedeo Avogadro believed that particles could be composed of molecules and that molecules could be composed of atoms.  The number of molecules in a mole was defined to be Avogadro's number.  Avogadro's number has been determined experimentally to be 6.0221415 x E-23 molecules per gram mole.