Mole (unit)
The mole ( unit symbol: mol) is the SI base unit of amount of substance used and the quantity stated in chemical reactions.
- 7.1 The mass of 1 mole of helium
- 7.2 The mass of 1 mol of water
- 7.3 Production of lithium from lithium and water
Definition
In the SI unit system, the mole is a base unit and defined as follows:
In other words, have 12 grams of carbon -12 exactly the amount of substance mole One mole of atoms a natural carbon, however, due to the isotope mixture has a mass of 12.0107 grams. Particle number and amount of substance are proportional to each other, so that any one of these two variables can serve as a measure of the other.
The number of particles per mole mole ( Avogadro ) has the value:
One mole of a substance contains about 602 trillion ie particles of that substance.
Historical
The term " mole " was coined in 1893 by Wilhelm Ostwald and is probably derived from " molecule". In the SI is 1971 the mole was introduced as the basic unit. Thus, the scope of the SI was extended to the chemistry. Before establishment of the SI, the mole has been mostly viewed as a mass unit. Older names are gram-atom (only for members ) and gram molecule (only in compounds ). Thus in DIN 1310 "salary of solutions " from April 1927: "As mass units are used [ ... ] the mole, ie number of grams of the substance, such as its molecular weight indicating [ ... ] ". However, it was through the application of molecular " weight " here is a mass - no volume today - and described them as " amount of substance ". In today mol definition of SI, however, the amount of mass of particles and mass is formally clearly distinguished.
Decimal multiples
Common Decimal parts and multiples of the mole are:
Molar volume
The molar volume of a substance is a substance-specific property that specifies which volume fills one mole of a substance. For an ideal gas, that one mole under standard conditions ( 273.15 K, 101325 Pa) occupies a volume of 22.414 liters. For real gases, solids and liquids, the molar volume, however, is dependent on the material.
Molar mass
The molar mass M is the quotient of mass and amount of substance of a substance. In units of g / mol it has the same numerical value as the atomic mass, ie the mass of an atom, in u ( atomic mass unit ). Their meaning is equivalent to the previous " atomic weight " in chemistry.
Calculation of quantities
For the calculation, the following formula is used:
This refers to the amount of substance, the mass and the molar mass. can be taken for chemical elements table and calculates levels of such chemical compounds values of known composition.
The atomic mass, which is given for each chemical element in tables, refers to the natural isotopic mixture. Thus, for example u in atomic mass for carbon 12.0107. This value is, for example, for enriched in 13C material not apply. While stable elements, deviations from isotopic mixtures, as they occur in nature, are relatively low, the mixture of isotopes may be highly dependent on the origin and age of the material, especially in the case of radioactive elements.
Using the unit mole at concentration data
The unit is often used in molar units composed to specify concentrations (solutions, acid solutions, etc.). One of the most common uses is the x - molar solution ( in the x stands for any positive rational number). The importance
Examples
Mass of 1 mol of helium
Mass of 1 mol of water
Production of lithium from lithium and water
In the formation of LiOH two water molecules from two lithium atoms are separated into a respective H- and OH - part. Because each mole of any substance the same number of particles are present (see above), you need for example, 2 mol of lithium and 2 mol of water (or any other fuel in the 2:2 ratio).