molecular weight


molecular weight
the average weight of a molecule of an element or compound measured in units once based on the weight of one hydrogen atom taken as the standard or on 1/16 the weight of an oxygen atom, but after 1961 based on 1/12 the weight of the carbon-12 atom; the sum of the atomic weights of all the atoms in a molecule. Abbr.: mol. wt. Also called formula weight.
[1875-80]

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Mass of a molecule of a substance, based on 12 as the atomic weight of carbon-12.

It is calculated in practice by summing the atomic weights of the atoms making up the substance's molecular formula. The molecular weight of a hydrogen molecule (chemical formula H2) is 2 (after rounding off); for many complex organic molecules (e.g., proteins, polymers) it may be in the millions.

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Universalium. 2010.

Look at other dictionaries:

  • Molecular weight — Molecular Mo*lec u*lar, a. [Cf. F. mol[ e]culare. See {Molecule}.] (Phys. & Chem.) Pertaining to, connected with, produced by, or consisting of, molecules; as, molecular forces; molecular groups of atoms, etc. [1913 Webster] {Molecular… …   The Collaborative International Dictionary of English

  • molecular weight — n the mass of a molecule that may be calculated as the sum of the atomic weights of its constituent atoms * * * the weight of a molecule of a substance as compared with that of an atom of carbon 12; it is equal to the sum of the atomic weights of …   Medical dictionary

  • molecular weight — n. the relative average weight of a molecule of a substance, expressed by a number equal to the sum of the atomic weights of all atoms in the molecule …   English World dictionary

  • molecular weight — UK / US noun [countable/uncountable] Word forms molecular weight : singular molecular weight plural molecular weights science the total of the atomic weights of all the elements in a compound …   English dictionary

  • molecular weight — santykinė molekulinė masė statusas T sritis Standartizacija ir metrologija apibrėžtis Molekulės vidutinės masės arba tiksliai apibrėžto medžiagos darinio masės ir nuklido ¹²C atomo masės 1/12 dalies dalmuo. atitikmenys: angl. molecular mass;… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • molecular weight — santykinė molekulinė masė statusas T sritis Standartizacija ir metrologija apibrėžtis Molekulę sudarančių atomų santykinių atominių masių suma, skaitine verte lygi medžiagos molio masei. atitikmenys: angl. molecular mass; molecular weight;… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • molecular weight — santykinė molekulinė masė statusas T sritis chemija apibrėžtis Molekulę sudarančių atomų santykinių atominių masių suma, skaitine verte lygi vieno medžiagos molio masei. atitikmenys: angl. molecular mass; molecular weight; relative molecular mass …   Chemijos terminų aiškinamasis žodynas

  • molecular weight — (MW)    The sum of the atomic weights of all of the atoms within a molecule. Generally, molecules of the same type have higher boiling points if the molecular weight is higher …   Forensic science glossary

  • molecular weight — weight of a molecule …   English contemporary dictionary

  • molecular weight — molec′ular weight′ n. chem. the average weight of a molecule of an element or compound measured in units based on 1/12 the weight of the carbon 12 atom; the sum of the atomic weights of all the atoms in a molecule. Abbr.: mol. wt • Etymology:… …   From formal English to slang


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