THE constant of THEvogador is simply the amount or number of elementary entities or particles (atoms, molecules, ions, electrons, protons) present in 1 mol of any matter (that which occupies space and has mass).
the italian chemist Lorenzo Romano Amedeo Carlo Avogadro (1776-1856) proposed, from his studies, that a sample of a element or substance, with mass in grams numerically equal to its atomic mass, would always have the same number of entities or particles.
Thus, for every 1 mole of the element nitrogen, we would have a mass in grams x, which would be related to a y number of atoms. Now, if we had 1 mole of nitrogen gas (N2), we would have a mass in grams z, related to a number y of molecules.
1 mole of the element N = y atoms;
1 mole of N atoms = y protons;
1 mole of atoms of N = y electrons;
1 mole of atoms of N = y neutrons;
1 mole of N2 = y molecules.
To facilitate the understanding proposed by Avogadro, the scientists, having technological development, with a technique called X-ray diffraction, were able to determine the amount of particles or entities present in a mole, whose value is 6,22.10
23.Therefore, it was not Avogadro who determined the quantity of particles. THE Avogadro's constant it was named after him. The most relevant thing, however, is that, whenever the term mol appears, the value 6.22.1023 must be used, such as:
1 mole of the element N = 6.22.1023 atoms;
1 mole of N atoms = 6.22.1023 protons;
1 mole of N atoms = 6.22.1023 electrons;
1 mole of N atoms = 6.22.1023 neutrons;
1 mole of N2 = 6,22.1023 molecules.
In addition to being used in relation to entities or particles, we can use the Avogadro's constant to determine the mass and volume of a sample. Below are some examples of using the Avogadro constant.
1º Example - (Ufac) A container with 180 g of water has how many molecules of water? Given: (H=1), (O=16)
a) 3.0 x 1023
b) 6.0 x 1024
c) 6.0 x 1023
d) 3.0 x 1024
e) 3.0 x 1025
The exercise gives the mass of the substance and asks for the number of molecules present in it. To do this, just set up a simple rule of three, assuming that 1 mole of water has 18 grams, and that in this mass there are 6.02.1023 atoms:
Note: A molar mass of water is equal to 18 grams because it has two moles of hydrogen atoms (each with a mass of 1 g) and 1 mole of oxygen atom (with a mass = 16 g).
18 g of H2The 6.02.1023 H molecules2O
180 g of H2Ox molecules of H2O
18.x = 180. 6,02.1023
18x = 1083.6.1023
x = 1083,6.1023
18
x = 60.2.1023 H molecules2O
or
x = 6.02.1024 H molecules2O
2º Example - (Unirio-RJ) The normal concentration of the adrenaline hormone (C9H13AT THE3) in blood plasma is 6.0. 10-8 g/L. How many adrenaline molecules are contained in 1 liter of plasma?
a) 3.6. 1016
b) 2.0. 1014
c) 3.6. 1017
d) 2.0. 1014
e) 2.5. 1018
Exercise provides the concentration of the hormone adrenaline and asks for the number of molecules present in a liter of plasma. To do so, just set up a simple rule of three, assuming that 1 mole of adrenaline has 183 grams, and that in this mass there are 6.02.1023 molecules:
Note: A molar mass of adrenaline is equal to 183 grams because it has 9 moles of carbon atoms (each with a mass of 12 g), 13 moles of carbon atoms. hydrogen (each with a mass of 1 g), 1 mol of nitrogen atoms (each with a mass of 14 g) and 3 mol of oxygen atoms (with mass 16 g).
183 g of C9H13AT THE3 6,02.1023 C molecules9H13AT THE3
6,0. 10-8 g of C9H13AT THE3x C molecules9H13AT THE3
183.x = 6.0. 10-8. 6,02.1023
18x = 36.12.10-8.1023
x = 36,12.1023
183
x = 0.1973.1015 C molecules9H13AT THE3
or
x = 1,973.1014 C molecules9H13AT THE3
3º Example - (UFGD-MS) In a sample of 1.15 g of sodium, the number of existing atoms will be equal to: Data: Na = 23
a) 6.0. 1023
b) 3.0. 1023
c) 6.0. 1022
d) 3.0. 1022
e) 1.0. 1023
The exercise gives the mass of the element sodium and asks for the number of atoms present in that mass. To do this, just set up a simple rule of three, assuming that 1 mole has 23 grams, and that in this mass there are 6.02.1023 atoms:
23 g of Na 6.02.1023 Na atoms
1.15 g of Nax Na atoms
23.x = 1.15. 6,02.1023
23x = 6,923.1023
x = 6,923.1023
23
x = 0.301.1023 Na atoms
or
x = 3.01.1022 Na atoms
4º Example - (Mauá-SP) Taking into account the atomic numbers of hydrogen (1) and oxygen (8), determine the number of electrons in 18 g of water.
O atomic number of an atom indicates the number of electrons it has in its electrospheres. Therefore, hydrogen and oxygen, together in the water molecule, have 10 electrons (2 electrons referring to 2 hydrogens and 8 of oxygen).
As electrons are particles of the atom, and Avogadro's constant can be used to calculate this number, to determine the number of electrons in 18 g of water, we assume that 1 mole of water has 18 g (2 g for hydrogens and 16 g for oxygen) and 6,02.1023 molecules. Thus:
1 mole of H2O18 g6.02.1023 molecules x electrons
1 molecule10 electrons
x.1 = 6.02.1023.10
x = 6.02.1024 electrons
*Image credits: rook76 / Shutterstock
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/quimica/o-que-e-constante-avogadro.htm