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The mole is a unit of amount of substance used in chemistry and physics, such that the mass of one mole of a substance expressed in grams is numerically equal to the average mass of one of its particles expressed in daltons. That is, the molar mass of a chemical compound expressed in g/mol or kg/kmol is numerically equal to its average ...
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).
For convenience in avoiding conversions in the imperial (or US customary units), some engineers adopted the pound-mole (notation lb-mol or lbmol), which is defined as the number of entities in 12 lb of 12 C. One lb-mol is equal to 453.592 37 g‑mol, [6] which is the same numerical value as the number of grams in an international avoirdupois pound.
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 ...
Atomic number Element Molar mass Formal standard atomic weight s.a.w., formal short Note Z calculated; g·mol −1 A r, standard [2] A r, abridged and conventional [2]; C 9 H 8 O 4: 180.159 g·mol −1
The mole and the atomic mass unit (dalton) were originally defined in the International System of Units (SI) in such a way that the constant was exactly 1 g/mol, which made the numerical value of the molar mass of a substance, in grams per mole, equal to the average mass of its constituent particles (atoms, molecules, or formula units) relative ...
The most common use of 'Daltons' is as a synonym for g/mol. When someone talks about a 254 kDa protein, they mean it has a molecular mass of 254,000 g/mol. I think this article needs to make this clear.27.54.43.66 03:46, 28 May 2011 (UTC) The statement "Da = g/mol" occurs often in chemistry texts and elsewhere.