| 单词 | number-average |
| 释义 | > as lemmasnumber-average number-average n. Chemistry an average of some parameter of the molecules of a mixture calculated as an arithmetic mean with each individual molecule contributing equally, regardless of size; frequently attributive. ΘΚΠ the world > matter > chemistry > atomic chemistry > [adjective] > relating to molecules > average number-average1935 1935 Jrnl. Physical Chem. 39 165 For heterogeneous materials, different methods for determining molecular weights give different ‘average’ values. Thus, it may be shown that freezing point, osmotic pressure, and end-group methods, when applied properly to an ideal mixture, result in an average value defined by the expression Mn = 1/Σ (fi/Mi) where fi is the fractional weight of the constituent of molecular weight Mi in the mixture, and the summation is to be applied to all constituents present. This average may be designated as a ‘number-average molecular weight’. 1955 Jrnl. Polymer Sci. 17 263 Number average degrees of polymerization are used to calculate the rates of initiation and transfer in vinyl polymerizations, and the extent of reaction in polycondensations. 1991 Progress Polymer Sci. 16 115 The number-average molecular weight (Mn) increases in direct proportion to monomer conversion. < as lemmas |
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