Avogadro's law

principle, which in 1811 formulated the Italian chemist Amedeo Avogadro (1776-1856), reads as follows: under the same temperature and pressure, equal volumes of gases will contain the same number of molecules regardless of their chemical nature and physical properties.This number is the physical constant is numerically equal to the number of molecules, atoms, electrons, ions or other particles contained in one mole.Later, the hypothesis of Avogadro, confirmed by a large number of experiments, was considered for ideal gases with one of the basic laws, which came into science called Avogadro's law and its consequences are all based on the assertion that the mole of any gas in the case of identical conditions, will occupy the same volume,called molar.

Sam Amadeo Avogadro assumed that the physical constant is a very large quantity, but many independent methods, after the death of the scientist allowed to establish experimentally the number of atoms contained in 12 g (is the atomic mass unit of carbon) or a molar volume of gas (atT = 273.15 K and p = 101.32 kPa) is equal to 22.41 liters.The constant is denoted as NA or less L. It is named after the scientist - the Avogadro constant, and is equal to it, approximately, 6,022 • 1023. This is the number of molecules of any gas in the volume of 22.41 liters, and it is the same for lightgas (hydrogen) and heavy gas (carbon dioxide).Avogadro's law can be expressed mathematically: V / n = VM, where:

  • V - volume of gas;
  • n - amount of substance that is the ratio of the mass of the substance to its mass molar;
  • VM - the constant of proportionality or the molar volume.

Amadeo Avogadro belonged to a noble family living in the northern part of Italy.He was born on 08.09.1776 in Turin.His father - Filippo Avogadro - was an employee of the Department of Justice.Last name medieval Venetian dialect means a lawyer or a bureaucrat who interact with people.According to existing tradition in those days, positions and professions were handed down.Therefore, in 20 years, Amadeo Avogadro received a degree and became a doctor of jurisprudence (the church).Physics and mathematics, he began to study on their own in 25 years.In his scientific work he studied electrical phenomena and research in the field of electrochemistry.However, in the history of science Avogadro went in to making the atomic theory is a very important addition: introduced the concept of the smallest particles of matter (molecules) that can exist independently.It was important to explain the relationship between the volume of simple gases, unreacted, and Avogadro's law began to have great importance for the development of science and is widely used in practice.

But this was not right.Some chemists Avogadro's law was voted through the decades.Opponents of the Italian physics professor beating such famous and recognized scientific authorities as Berzelius, Dalton, Davy.Their mistakes have led to years of disputes about the chemical formula of the water molecule, as it was felt that it should be written not H2O, or HO and H2O2.Only Avogadro's law has helped to establish the composition of the molecules of water and other simple and complex substances.Amadeo Avogadro argued that the molecules of simple elements consist of two atoms: O2, H2, Cl2, N2.Which meant that the reaction between hydrogen and chlorine as a result of which will be formed hydrogen chloride, can be written as: Cl2 + H2 → 2HCl.The interaction of one molecule to one molecule Cl2 H2, form two molecules of HCl.The volume, which will occupy HCl, must be twice the volume of each of the joined the reaction components, i.e. they must be equal to the total volume.Only since 1860, has been actively used Avogadro's law, and the consequences from it possible to establish the true values ​​of the atomic weights of some chemical elements.

One of the main conclusions reached at its base, was the equation that describes the state of an ideal gas: p • VM = R • T, where:

  • VM - molar volume;
  • p - gas pressure;
  • T - the absolute temperature, K;
  • R - the universal gas constant.

combined gas law as a consequence of Avogadro's law.At a constant mass of matter looks like (p • V) / T = n • R = const, and his notation: (p1 • V1) / T1 = (p2 • V2) / T2 allows you to make payments when moving gas from one state(marked by 1) to another (with index 2).

Avogadro's law led to the second important conclusion opens the way for the experimental determination of the molecular weight of the substances that the transition to the gaseous state do not decompose.M1 = M2 • D1, where:

  • M1 - the molar mass of the first gas;
  • M2 - the molar mass of the second gas;
  • D1 - relative density of the first gas, which is mounted on the air or hydrogen (hydrogen: D1 = M1 / ​​2, the air D1 = M1 / ​​29, where 2 and 29 - is the molar mass of hydrogen and air, respectively).