Molar mass of oxygen. What is the molar mass of oxygen?

Atoms of elements and molecules of substances possess negligible low mass. To study the quantitative relationships characteristic of chemical reactions, several physical quantities are used. One of them is the molar mass, which can be calculated for atoms, ions and molecules. One of the most important elements on Earth is oxygen, many reactions and processes take place with its participation. To perform calculations using the formula of compounds, the reaction equations use the molar mass of oxygen, which is numerically equal to the relative mass of its atom or molecule.

Oxygen

General information about oxygen (chemical element):

• Latin name - Oxygenium;
• Chemical symbol - O;
• Is located in the upper part of the 16th group (formerly group VI A) of the periodic table;
• Is located in the second period immediately after nitrogen, before fluoride;
• Belongs to the family of chalcogenes;
• The number of the element in the periodic table and the charge of the nuclei of its atoms is 8.

Oxygen as one of the components of the atmosphere for a long time could not be isolated in its pure form. The gas was called "life-giving", "the elixir of life." Honor of the discovery of oxygen is shared among themselves by scientists with a worldwide reputation: K. Scheele, J. Priestley, A. Lavoisier. The term "oxigen" was suggested by A. Lavoisier, starting from the important role of matter, its atoms in the formation of oxides and acids.

How to find the molar mass of an element or substance?

When performing chemical calculations, it is necessary to know the masses of the atoms and molecules involved in the reactions. But they are too small, which makes it difficult to use units such as grams and kilograms. The output was found: other quantities were proposed to facilitate calculations. For example, in chemistry, the relative values of atomic and molecular weights are used. The relative mass of the atom (Ar) as a physical quantity was introduced in 1961. Its value is equal to 1/12 of the mass of the carbon atom (isotope ¹² C).

To perform calculations using formulas and equations using this and other variables, several rules must be remembered:

1. The mass of the atom is indicated in the periodic table next to the chemical sign. The molar mass has the same numerical value, but with units of measurement g / mol.
2. The mass of one mole of substance is determined by the formula of the compound, for which the sum of the molar masses of all particles in the molecule is found.
3. If the chemical formula has an index indicating the number of structural units, then it is necessary to multiply the molar mass by this coefficient.

Atomic and molecular weight of oxygen

The mass of the oxygen atom is obtained taking into account the amount and distribution of its three natural isotopes: Ar (O) = 15.999 (in ae m). In calculations this value is usually rounded, it turns out 16. For each element, its atomic mass is a constant value. According to the known mass of the atoms of the element with the ordinal number 8, the molar mass of the oxygen element can be found. M (O) = 16. Another dimensionless physical quantity, the molecular mass of oxygen, refers to a simple substance. Calculate the mass of the oxygen molecule by multiplying the mass of the atom by the stoichiometric coefficient in the formula: Mr (O2) = Ar (O) ^. 2 = 16 ^. 2 = 32. In practice, there is no need to find out what is the molar mass of oxygen, because its value is numerically equal to the mass of the molecule of the substance, but with the unit of measure r / mol. For a specific compound, its molecular weight is a constant, widely used in calculating the amount and mass of matter.

Amount of substance

In chemistry, for the convenience of calculations, one of the most important physical quantities is the quantity of matter. It does not refer to the mass, but to the number of structural units. A unit of measurement of the amount of a substance in the International System (SI) is 1 mole. Knowing that 1 mole contains as many particles as they are contained in 12 g of the carbon isotope ¹² C, it is possible to calculate the number of atoms, molecules, ions, electrons contained in the sample of any substance. Another constant value is named in honor of the great Italian scientist Avogadro (denoted by NA), It characterizes the number of structural particles that contain a substance, if its amount is 1 mole. The numerical value of Avogadro's constant is 6.02 ^. 10 ²³ 1 / mol. It is this number of atoms (molecules, ions) that has a molar mass. The designation of this physical quantity is M, the unit of measurement is 1 g / mol, the formula for calculation is M = m / n (m is the mass (g), n is the amount of substance (mole)).

What is the molar mass of oxygen

In practice, there is no need to use the formula M = m / n to calculate the molar mass of oxygen. When solving problems, it is often necessary to determine what the mass is equal to, or to find the amount of matter. In the first case, the formula m = n is used for calculations ^. M, in the second - n = m / M. The numerical value of the molar mass of the element coincides with the mass of the atom, and for the substance - molecules. For example, a mass of 16 grams has 1 mole of oxygen. M (O ₂ ) is the molar mass of the oxygen molecule, which is 32 g / mol.

The molar mass of the oxygen equivalent

Equivalent is the value equal to the mass of 1 mole of atoms of any monovalent element. In the general case, it is possible to determine the equivalent mass by dividing the molar mass of the atoms of a chemical element by its valence, found by the formula of a particular compound. In most of its compounds, oxygen, as a chemical element-chalcogen, is bivalent. The molar mass of oxygen can be found from the Mendeleyev table, its rounded value is 16. The equivalent mass is 2 times less than 8. The chemistry uses the law of equivalents, which states that substances react with each other in quantities equal to their equivalents. When performing calculations, you can use the molar mass of the equivalent of oxygen to determine the mass of the equivalent of the substance for which it is unknown.

Oxygen is one of the most important elements in the earth's crust, accounting for 46.6% of the mass. A simple connection with the same name is the second most common in the Earth's atmosphere. The content of molecular oxygen in the air is 20.947% by volume. With the participation of atoms of the element and molecules of matter, many reactions and processes occur in engineering, industry, living and inanimate nature. It is important to take into account the quantitative relationships in these processes, which greatly facilitates the use of physical quantities, including the molar mass of oxygen.