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Avogadro’s Law

Avogadro’s law, put forward in 1811 by an Italian scientist named Avogadro states: Equal volumes of all gasses at the same temperature and pressure contain the same number of molecules.

The importance of this law is that it enables the volumes of gases in chemical reactions to be converted directly to actual molecules contained. And since molecules are involved in chemical reactions, the law gives a deeper understanding about chemical reactions in gases, and allows the deductions of Gay- Lusac’s law.

Notice that this law is applicable only to gases.

Example: 2 volumes of hydrogen combine with 1 volume of oxygen to give 2 volumes of steam at constant temperature and pressure. This can be read as: 2 molecules of hydrogen combine with 1 molecule of oxygen to give 2 molecules of steam.