From the school chemistry course, we know that if we take one mole of a substance, it is 6.02214084 (18) • 10 ^ 23 atoms, or other structural elements (molecules, ions, etc.).For the convenience of Avogadro's number is usually written as such: 6.02 • 10 ~ 23.
But why Avogadro constant (in the Ukrainian language "became Avogadro") is precisely such a value?The answer to this question is not in the textbooks, and historians of chemistry offers a variety of versions.It seems that the Avogadro number is a secret meaning.Surely there must be magic numbers, which include some number of "pi" Fibonacci numbers, seven (eight in the east), 13, etc.We will fight to the information vacuum.About who this Amedeo Avogadro, and why in honor of the scientist in addition he formulated the law, found constant was also named a crater on the moon, we will not speak.It was already written a number of articles.
be precise, Amedeo Avogadro was not engaged in calculations of molecules or atoms in any particular volume.The first who tried to figure out how much of the gas molecules contained in a given volume at the same pressure and temperature, was Joseph Loschmidt, and that was in 1865.As a result of his experiments Loschmidt concluded that in one cubic centimeter of any gas under normal conditions is 2.68675 • 10 ^ 19 molecules.
was subsequently invented a large number of independent ways of how to determine the Avogadro constant, and since the results in most of the match, it is once again spoke in favor of the real existence of molecules.At the moment, the number exceeded 60 methods, but in recent years, scientists are trying to further improve the accuracy of the estimate, to introduce a new definition of the term "kilogram".So far, the kilogram is associated with the selected standard material without any fundamental definitions.
But back to our original question - why this constant is equal to 6.022 • 10 ~ 23?
in Chemistry in 1973, for convenience in the calculations was proposed to introduce such a concept as "amount of substance".The basic unit of measure for the amount of steel mol.According to the recommendations of the IUPAC, the amount of any substance is proportional to the number of its specific elementary particles.The proportionality factor is not dependent on the type of substance and the Avogadro's number is its inverse value.
For clarity, let us take some example.As is known from the definition of atomic mass unit 1 amuIt corresponds to one-twelfth the mass of a carbon atom and 12C is 1.66053878 • 10 ^ (- 24) grams.If you multiply 1 amuAvogadro constant on, it will turn out 1,000 g / mol.Now take some chemical element, for example, beryllium.According to the table of the mass of one atom of beryllium is 9.01 amuCalculate what is one mole of atoms of that element:
6.02 x 10 ^ 23 mol-1 * 1.66053878h10 ^ (- 24) g * 9.01 = 9.01 grams / mole.
Thus, it turns out that the molar mass is numerically equal to the atomic.
Avogadro constant has been specially selected to match the atomic molar mass of any dimensionless quantity - relative molecular (atomic) weight.We can say that the number of Avogadro owes its appearance on the one hand, the atomic mass unit, and the other - the standard unit for comparing weight - grams.
