- - periodic table of chemical elements;
- - scales;
- - Calculator.
Knowing this value, the amount of material ν, find the number of molecules it.For this amount of material measured in moles, multiply by Avogadro constant (NA = 6,022 ∙ 10 ^ 23 January / mol), which is equal to the number of molecules 1 mole of substance N = ν / NA.For example, if you have 1.2 moles of salt, then it contains N = 1,2 ∙ 6,022 ∙ 10 ^ 23 ^ 10 ≈7,2 ∙ 23 molecules .
If you know the chemical formula of the substance, with the help of the periodic table of elements, locate it molar mass.To do this on the table for the relative atomic mass of the atoms that make up molecules well, and add them.The result is a r
elative molecular yarnuyu mass of matter which is numerically equal to its molar weight in grams per mole.Then, on the scales measure the weight of the substance in grams.To find the number of molecules in matter , multiply the weight of the substance m on the Avogadro constant (NA = 6,022 ∙ 10 ^ 23 January / mol) and divide the result by the molar mass M (N = m ∙ NA / M).
Example Determine the number of molecules , which is contained in 147 g of sulfuric acid.Find the molar mass of sulfuric acid.Its molecular and consists of 2 hydrogen atoms and one sulfur atom 4 oxygen atoms.Their atomic weights are 1, 32 and 16. The relative yarnaya molecular weight is 2 ∙ 1 + 32 + 16 = 4 ∙ 98.It is equal to the molar mass, thus M = 98 g / mol.Then the number of molecules , contained in 147 g of sulfuric acid will be equal to N = 147 ∙ 6,022 ∙ 10 ^ 23 / 98≈9 ∙ 10 ^ 23 molecules .
To find the number of molecular gas in normal conditions at a temperature of 0 ° C and a pressure of 760 mm Hg.column, find its volume.To do this, measure or calculate the volume of the container V, in which he is in liters.To find the number of molecules divide the gas volume of 22.4 liters (volume of one mole of gas under normal conditions), and multiply by Avogadro's number (NA = 6,022 ∙ 10 ^ 23 January / mol) N = V ∙ NA / 224.
- how to determine the number of molecules