The term "molar mass of a substance" is understood to mean the mass of one of its moles, that is, of an amount of matter that contains 6.022x10 ^ 23 atoms, ions or molecules.
This mass is measured in grams / mole.
How can we calculate the molar mass of a complexSubstance? Calculate the molar mass of the substance is very simple; it requires only knowing its formula. In order to understand how this value is calculated, consider, for example, ammonium nitrate, well familiar to some growers, used as an effective and cheap nitrogen fertilizer. The more accurate name of this substance in accordance with the requirements of the chemical nomenclature is ammonium nitrate. The chemical formula of ammonium nitrate is as follows: NH4NO3. That is, in its one molecule contains 2 nitrogen atoms, 4 hydrogen atoms and 3 oxygen atoms. And what is its total molecular weight? To determine it, you need to multiply the atomic masses of each element by the number of atoms and add the resulting products.
The atomic mass of nitrogen is 14 atomic units,Hydrogen - 1, oxygen - 16. Make a simple calculation: 2x14 + 1x4 + 3x16. Get the result: 28 + 4 + 48 = 80 atomic mass units. This is the molecular weight of ammonium nitrate. For calculations, rounded values of the atomic masses of the elements were used.
And since a mole is a quantity of matter,The mass of which, expressed in grams, is numerically equal to its molecular mass in atomic units, then you immediately get the result: 1 mole of ammonium nitrate is approximately 80 grams. This is the molar mass of this substance.
What are the molar masses of simple substances? Not all chemical substances are complex, that is, they consist of different atoms. How to calculate the molar mass of a substance consisting of atoms of only one species, for example graphite or diamond containing only carbon (C)? This task will not be the slightest effort. It is only necessary to know the atomic mass of the element. In carbon it is 12 atomic mass units, therefore, the molar mass of both diamond and graphite is 12 grams / mole.
If the molecules of simple substances are not composed of 1Atom, and from several, the atomic mass of the element is multiplied by the corresponding coefficient. For example, O2 is the formula of a known oxygen gas, due to which there is life on Earth. Its molar mass is 16x2 = 32 grams / mole. But the formula for its modification, ozone - gas with a characteristic sharp odor - O3. Consequently, the molar mass of ozone is 16x3 = 48 grams / mole.