molecular weight 名詞



 Mo·lec·u·lar a.  Phys. & Chem. Pertaining to, connected with, produced by, or consisting of, molecules; as, molecular forces; molecular groups of atoms, etc.
 Molecular attraction Phys., attraction acting between the molecules of bodies, and at insensible distances.
 Molecular weight Chem., the weight of a molecule of any gas or vapor as compared with the hydrogen atom having weight of 1 as a standard; the sum of the atomic weights of the constituents of a molecule; thus, the molecular weight of water (H2O) is 18.  For more precise measurements, the weight of the carbon isotope carbon-12 is used as the standard, that isotope having the value of 12.000.  In this systen, now used almost universally, the hydrogen atom has a weight of 1.0079.

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 molecular weight
      n : (chemistry) the sum of the relative atomic masses of the
          constituent atoms of a molecule [syn: {relative molecular
          mass]