Avogadro's law says that identical volumes of ideal gases with an identical pressure and identical temperature contain equal number of molecules. Otherwise it is possible to tell that one mol of any gas with an identical pressure and temperature occupies the same volume. Avogadro's number is a physical quantity which is in number equal to the number of structural units in 1 mole of a substance. Any particles - atoms, molecules, electrons, ions, etc. can be structural units.
Instruction
1. Tried to determine by the first quantity of molecules of gases at an identical temperature and pressure in the same volume Josef Loschmidt in 1865. After that a large number of independent methods of definition of number of Avogadro was developed. Coincidence of values is the evidence of real existence of molecules.
2. Mol – amount of substance which contains as much structural units how many contains in 12 grams isotopeof carbon ^12С. For example, the same 12 grams of isotope of carbon ^12С contain 6.022•10^23 of carbon atoms, or exactly 1 mol. Weight of 1 mole of a substance is expressed by the number of grams which to equally molecular mass of this substance.
3. One of the most exact methods of definition of number of Avogadro is the definition based on measurement of a charge of an electron. Faraday's number - one of physical constants equal to the work of number of Avogadro on elementary electric charge. F = N (A) e where F is Faraday's number, N (A) is Avogadro's number, e – an electron charge. Faraday's constant defines quantity of electricity which passing through solution of electrolyte leads to allocation on an electrode 1 mol of monovalent substance.
4. Faraday's number can be found, measuring quantity of electricity necessary for sedimentation of 1 mol of silver. It was by practical consideration established that value F = 96490.0 C, and an electron charge e = 1.602Ч10^-19Кл. From here it is possible to find N (A).
5. By modern science with high precision it is defined that number of the structural units which are contained in 1 mole of a substance or Avogadro's number of N (A) = (6.022045 ± 0.000031)Ch10^23. Avogadro's number – one of fundamental constants allowing to determine such sizes, as an electron charge, mass of atom or a molecule, etc.