elements Atoms and molecules have negligible mass.To study the quantitative relations characteristic of chemical reactions, using several physical quantities.One of them - the molar mass, which can be calculated for atoms, ions and molecules.One of the most important elements on Earth - the oxygen flow to his participation many reactions and processes.To perform calculations using formulas of compounds, reaction equations using the molar mass of oxygen which is numerically equal to the relative weight of its atom or molecule.
Oxygen
Understanding oxygen (chemical element):
- Latin name - Oxygenium;
- chemical symbol - O;
- at the top of the 16th group (previously - Group VI A) of the periodic table;
- located in the second period immediately after the nitrogen to fluorine;
- belongs to the family chalcogen;
- number of the element in the periodic table and the charge of the nuclei of its atoms - 8.
Oxygen as one of the components of the atmosphere for a long time could not be purified.Gas called "life-giving", "the elixir of life."The honor of opening the oxygen is divided between the scientists of world renown: K. Scheele, John. Priestley, Antoine Lavoisier.The term "oxygenation" Lavoisier proposed, based on the importance of the substance, its atoms in the formation of oxides and acid.
How to find the molar mass of an element or substance?
When performing chemical calculations need to know the mass involved in the reactions of atoms and molecules.But they are too small, which complicates the use of such units, as grams and kilograms.The solution was found: the value offered other to facilitate calculations.For example, in chemistry values are relative atomic and molecular mass.Relative atomic mass (Ar) as a physical quantity was introduced in 1961.Its value is equal to 1/12 of the mass of the atom (the isotope 12C).
to perform calculations using formulas and equations with the use of these and other variables need to remember a few rules:
- contains the mass of the atom in the periodic table near a chemical symbol.The molar mass has the same numerical value, but with the units g / mol.
- mass of one mole of a substance is determined by the formula of the compound, which are the sum of the molar masses of all particles in the molecule.
- If the chemical formula is the index indicating the number of structural units, it is necessary to increase the molar mass of this coefficient.
Atomic and molecular mass of oxygen
mass of an oxygen atom is obtained based on the number and distribution of its three natural isotopes: Ar (G) = 15,999 (in a. E. M.).In calculating this value is usually rounded, turns 16. For each element, its atomic weight - constant.According to a known mass of atoms of element 8 can be found molar mass of the element oxygen.M (G) = 16. Another dimensionless physical quantity - the molecular weight of oxygen - refers to the simple substance.Calculated molecular mass of oxygen atom on the weight multiplying stoichiometric coefficient in the formula: Mr (O2) = Ar (G).2 = 16.2 = 32. In practice, there is no need to find out what the molar mass of oxygen, because its value is numerically equal to the mass of molecules of the substance, but with the unit g / mol.For a particular compound is its molecular weight is constant, widely used in the calculation of the amount and weight of the substance.
number of substances in chemistry for the convenience of calculation is used, one of the most important physical quantities - the amount of substance.It refers not to the weight, and to the number of structural units.The unit of measurement of the amount of matter in the International System (SI) adopted on 1 mol.Knowing that 1 mol includes same particles as are contained in 12 g of carbon isotope 12 C can calculate the number of atoms, molecules, ions, electrons contained in the test portion of any substance.Another constant was named after the great Italian scientist Avogadro (designated NA) It characterizes the number of structural particles, which contains the substance, if the amount - 1 mol.The numerical value of the Avogadro constant - 6.02.1023 1 / mole.This is the number of atoms (molecules or ions) has a molar mass.Designation of the physical quantity - M unit - 1 g / mol, the formula for the calculation - M = m / n (m - weight (g), n - 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.In solving problems often need to determine what is the weight or amount of the substance found.In the first case is used for calculation formula m = n.M, in the second - n = m / M.The numerical value of the molar mass of the element coincides with the mass of the atom, as for the substance - a molecule.For example, the mass of 16 g is 1 mol element oxygen.M (O2) - the molar mass of a molecule of oxygen, which is equal to 32 g / mol.
molar mass equivalent oxygen
An equivalent is called an amount equal to the mass of one mole of any of the atoms of a monovalent element.In general, you can determine the equivalent weight by dividing the molar mass of the atoms of a chemical element in its valence, found the formula of the particular compound.In most of its oxygen compounds as a chemical element-chalcogen is divalent.The molar mass of oxygen can be found on the periodic table, her rounded value - 16. The equivalent weight of less than 2 times - 8. In chemistry, the law of equivalents, which states that the substances react with one another in amounts of cash equivalents.In your calculations, you can use the molar mass of oxygen equivalent to determine the equivalent weight of a substance for which it is known.
Oxygen - one of the most important elements in the earth's crust, accounting for 46.6% of the mass.Simple connection with the same name - the second most common in the Earth's atmosphere.The content of molecular oxygen in the air - 20.947% by volume.With the participation of member atoms and molecules occur, many reactions and processes in engineering, industrial, organic and inorganic nature.It is important to take into account the quantitative ratio in these processes, which greatly facilitates the use of physical quantities, including the molar mass of oxygen.
