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Molecular weight (M.W.) (for molecular compounds) and formula weight (F.W.) (for non-molecular compounds), are older terms for what is now more correctly called the relative molar mass (M r). [8] This is a dimensionless quantity (i.e., a pure number, without units) equal to the molar mass divided by the molar mass constant .
A Free Android application for molecular and reciprocal weight calculation of any chemical formula; Stoichiometry Add-In for Microsoft Excel Archived 2011-05-11 at the Wayback Machine for calculation of molecular weights, reaction coefficients and stoichiometry.
In practice, four averages are used, representing the weighted mean taken with the mole fraction, the weight fraction, and two other functions which can be related to measured quantities: Number average molar mass (M n), also loosely referred to as number average molecular weight (NAMW).
The molar mass constant, usually denoted by M u, is a physical constant defined as one twelfth of the molar mass of carbon-12: M u = M(12 C)/12. [1] The molar mass of an element or compound is its relative atomic mass (atomic weight) or relative molecular mass (molecular weight or formula weight) multiplied by the molar mass constant.
Chemical formula Molecular weight (MW) Valencies (V) Sample Reference Elemental mEq Elemental mEq to compound weight Potassium (reference) K 39.098 g/mol 1 (K +) 20 mEq potassium 20*39.098/1=782 mg Potassium citrate monohydrate C 6 H 7 K 3 O 8: 324.41 g/mol 3 (K +)
Whereas molecular weight (molar mass) for D-glucose monohydrate is 198.17 g/mol, [48] [49] that for anhydrous D-glucose is 180.16 g/mol [50] [51] [52] The density of these two forms of glucose is also different. [specify] In terms of chemical structure, glucose is a monosaccharide, that is, a simple sugar.
A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C 6 H 12 O 6 rather than the glucose empirical formula, which is CH 2 O. However, except for very simple substances, molecular chemical formulae lack needed structural information, and are ambiguous.
Mass fraction can also be expressed, with a denominator of 100, as percentage by mass (in commercial contexts often called percentage by weight, abbreviated wt.% or % w/w; see mass versus weight). It is one way of expressing the composition of a mixture in a dimensionless size ; mole fraction (percentage by moles , mol%) and volume fraction ...