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For example, 10 moles of water (a chemical compound) and 10 moles of mercury (a chemical element) contain equal numbers of substance, with one atom of mercury for each molecule of water, despite the two quantities having different volumes and different masses. The mole corresponds to a given count of entities. [5]
Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...
"The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 10 23 elementary entities. This number is the fixed numerical value of the Avogadro constant, N A, when expressed in the unit mol −1 and is called the Avogadro number.
In the International System of Units (SI), the coherent unit for molar concentration is mol/m 3. However, most chemical literature traditionally uses mol/dm 3, which is the same as mol/L. This traditional unit is often called a molar and denoted by the letter M, for example: 1 mol/m 3 = 10 −3 mol/dm 3 = 10 −3 mol/L = 10 −3 M = 1 mM = 1 ...
One entity, symbol ent, is the smallest amount of any substance (retaining its chemical properties). One mole is an aggregate of an Avogadro number of entities, 1 mol = N 0 ent. This means that the appropriate atomic-scale unit for molar mass is dalton per entity, Da/ent = M u, very nearly equal to 1 g/mol.
The mole was defined in such a way that the molar mass of a compound, in g/mol, is numerically equal to the average mass of one molecule or formula unit, in daltons. It was exactly equal before the redefinition of the mole in 2019 , and is now only approximately equal, but the difference is negligible for all practical purposes.
For example, water has a molar mass of 18.0153(3) g/mol, but individual water molecules have molecular masses which range between 18.010 564 6863(15) Da (1 H 2 16 O) and 22.027 7364(9) Da (2 H 2 18 O). Atomic and molecular masses are usually reported in daltons, which is defined in terms of the mass of the isotope 12 C (carbon-12).
The mole is a unit of measurement that denotes an amount of substance (also called chemical amount). One mole is defined to contain exactly 6.022 140 76 × 10 23 particles (atoms, molecules, ions, or electrons), where the number of particles per mole is known as the Avogadro constant. [27]