Amedeo Avogadro Italian physicist who originated the
hypothesis that the equal volumes of all gasses, under the
same pressure and temperature conditions, contain the
same number of molecules. Avogadro made this hypothesis
in 1811. It has since been fully proven and is now known as
Avogadros law.


Avogadro was born in Turin, Italy, an August 9th,
1776, to an artistic family. Avogadro practiced law and
then studied physics and mathematics. He was appointed
professor of physics at Vercelli in 1809. In 1811 he set
forth his famous hypothesis, now known as Avogadros law.

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The law stated that equal volumes of all gasses at the same
temperature and pressure contain the same number of
molecules. Avogadros law helped overcome flaws in John
Daltons atomic theory. Avogadro also distinguished
between an atom and a molecule, and made it possible to
determine a correct table of atomic weights. The correction
and standardization of atomic weights began in 1858 when
Stanislao Cannizzaro, an Italian chemist, reminded other
chemists about Avogadros work. The hypothesis was
virtually ignored by chemists because when it was tested in
1881 appropriate temperatures were not used by other
scientists.


6.0221367 x10 23
Avogadros number stated that a mole of any
substance is that quantity of the substance that weighs (in
grams) the same as its molecular weight. For example,
molecular oxygen, has a weight of 32 grams (16 for each
oxygen atom); one mole of oxygen weighs 32 grams. A mole
of a substance always contains the same number molecules
–the Avogadros lawas a mole of any substance.


Therefore, Avogadros law can be stated in terms of moles,
namely that equal volumes of gases at the same
temperature and pressure contain the same number of
molecules by simply weighing out an equal number of
moles. Avogadros number itself holds true for all
substances, what ever there state.

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