Avogadro's law opened in 1811 is one of basic provisions of chemistry of ideal gases. It says: "Equal volumes of ideal gases with an identical pressure and temperature contain identical number of molecules".
Concept and constant Avogadro's value
The physical quantity equal to quantity of structural elements (which molecules, atoms, etc. are) on one mole of a substance, is called Avogadro's number. Its value which is officially accepted today is NA = 6.02214084(18) ×1023 моль−1, it was approved in 2010. In 2011, results of new researches were published, they are considered as more exact, but at the moment are officially not approved.
Avogadro's law has huge value in development of chemistry, he allowed to calculate the weight of bodies which can change a state, becoming gaseous or vaporous. On the basis of Avogadro's law there began the development the atomic and molecular theory following from the kinetic theory of gases.
Moreover, by means of Avogadro's law the way of obtaining molecular mass of the dissolved substances is developed. For this purpose laws of ideal gases were distributed also to the diluted solutions, having taken a thought as a basis that the dissolved substance will be distributed on solvent volume as gas is distributed in a vessel. Also Avogadro's law gave the chance to determine true atomic masses of a number of chemical elements.
Practical use of number of Avogadro
The constant is used when calculating chemical formulas and in the course of drawing up the equations of chemical reactions. Determine the relative molecular mass of gases and number of molecules in one pier of any substance by it. Through Avogadro's number the universal gas constant is calculated, it turns out by multiplication of this constant by Boltzmann's constant. Besides, having increased Avogadro's number and elementary electric charge, it is possible to receive Faraday's constant.
Use of the investigations of the law of Avogadro
The first investigation of the law says: "One mol of gas (any) under equal conditions will occupy one volume". Thus, in normal conditions the volume of one of any gas it is equal 22.4 liters (this size is called the molar volume of gas), and using Mendeleyev-Klapeyrona's equation it is possible to determine gas volume with any pressure and temperature. The second investigation of the law: "The molar mass of the first gas is equal to the work of molar mass of the second gas on the relative density of the first gas to the second". In other words, under identical conditions, knowing the relation of density of two gases, it is possible to determine their molar masses. At the time of Avogadro his hypothesis was unprovable theoretically, however allowed to establish easily experimentally structure of molecules of gas and to determine their weight. Over time under its experiments the theoretical base was failed, and now Avogadro's number finds application in chemistry.