Avogadro practiced law andthen studied physics and mathematics. He was appointedprofessor of physics at Vercelli in 1809. In 1811 he setforth his famous hypothesis, now known as Avogadros law. The law stated that equal volumes of all gasses at the sametemperature and pressure contain the same number ofmolecules.
Avogadros law helped overcome flaws in JohnDaltons atomic theory. Avogadro also distinguishedbetween an atom and a molecule, and made it possible todetermine a correct table of atomic weights. The correctionand standardization of atomic weights began in 1858 whenStanislao Cannizzaro, an Italian chemist, reminded otherchemists about Avogadros work. The hypothesis wasvirtually ignored by chemists because when it was tested in1881 appropriate temperatures were not used by otherscientists. 6. 0221367 x10 23Avogadros number stated that a mole of anysubstance is that quantity of the substance that weighs (ingrams) the same as its molecular weight.
For example,molecular oxygen, has a weight of 32 grams (16 for eachoxygen atom); one mole of oxygen weighs 32 grams. A moleof 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 sametemperature and pressure contain the same number ofmolecules by simply weighing out an equal number ofmoles. Avogadros number itself holds true for allsubstances, what ever there state.