|
( Mole (unit))
The mole (symbol mol) is a unit of amount of substance it is an SI base unit,[1] and almost the only unit to be used to measure this physical quantity. The name "mole" was coined in German (as Mol) by Wilhelm Ostwald in 1893,[2] although the related concept of equivalent mass had been in use at least a century earlier. The name is assumed to be derived from the word Molekül (molecule). The first usage in English dates from 1897, in a work translated from German.[3][4] The names gram-atom and gram-molecule have also been used in the same sense as "mole",[1][5] but these names are now obsolete. The mole is defined as the amount of substance of a system which contains as many "elemental entities" (e.g., atoms, molecules, ions, electrons) as there are atoms in 12&_160;g of carbon-12.[1] Hence It is a common misconception that the mole is defined in terms of the Avogadro constant (also, anachronistically, known as "Avogadro's number"). It is not necessary to know the number of atoms or molecules which are present in order to use the mole as a unit of measurement,[5] and indeed the first measurements of amount of substance predate modern atomic theory and any measurements of atomic weight.[6] The current definition of the mole was approved during the 1960s[1][5] Prior to that, there had been definitions based on the atomic weight of hydrogen, the atomic weight of oxygen and the relative atomic mass of oxygen-16 the four different definitions are equivalent to within 1%. The most common method of measuring an amount of substance is to measure its mass and then to divide by the molar mass of the substance.[7] Molar masses may be easily calculated from tabulated values of atomic weights and the molar mass constant (which has a convenient defined value of 1&_160;g/mol). Other methods include the use of the molar volume or the measurement of electric charge.[7]
|
Mole (unit) Subcategories
Mole (unit) Articles
|
| 
