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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 .
Assuming the unknown compound behaves as an ideal gas, the number of moles of the unknown compound, n, can be determined by using the ideal gas law, p V = n R T {\displaystyle pV=nRT\,} where the pressure, p , is the atmospheric pressure , V is the measured volume of the vessel, T is the absolute temperature of the hot bath, and R is the gas ...
In mass spectrometry, the molecular mass of a small molecule is usually reported as the monoisotopic mass: that is, the mass of the molecule containing only the most common isotope of each element. This also differs subtly from the molecular mass in that the choice of isotopes is defined and thus is a single specific molecular mass out of the ...
The exact mass of an isotopic species (more appropriately, the calculated exact mass [9]) is obtained by summing the masses of the individual isotopes of the molecule. For example, the exact mass of water containing two hydrogen-1 ( 1 H) and one oxygen-16 ( 16 O) is 1.0078 + 1.0078 + 15.9949 = 18.0105 Da.
In the spectrum for toluene for example, the molecular ion peak is located at 92 m/z corresponding to its molecular mass. Molecular ion peaks are also often preceded by an M-1 or M-2 peak resulting from loss of a hydrogen radical or dihydrogen, respectively. Here, M refers to the molecular mass of the compound.
Size-exclusion chromatography, also known as molecular sieve chromatography, [1] is a chromatographic method in which molecules in solution are separated by their shape, and in some cases size. [2] It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers . [ 3 ]
This template calculates the molecular mass (or molar mass) of a chemical compound. It is designed to be embedded in infoboxes {{ Infobox drug }} and {{ Chembox }} , but it can be used in-line just as well.
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.