Molar mass

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Molar mass is the mass of one mole of a chemical element or chemical compound.

A mole is defined as Avogadro's number, approximately 6.022x10²³, of particles of any kind of substance (atoms, ions, molecules, or formula units).

In chemistry, the unit is g/mol, although the International System unit is kg/mol. The atomic mass listed for the elements on the periodic table can be interpreted in two ways: first as the mass of a single average atom of the element in unified atomic mass units (u), or secondly as the mass of one mole of the element in grams. This second use is the molar mass of the element and is most useful in stoichiometric calculations. In physics, molar mass is usually defined in kilograms per kilomole (kg/kmol). Molar mass is different from Molecular mass which is the mass of one molecule.

In linear polymers not every polymer chain consists of the same amount of repeating units. A given polymer sample is said to be made up of a mixture of macromolecules with a certain molar mass distribution.

[edit] Example

Let us see how many grams are in one mole of table sugar with a chemical formula of <math>{}^{12}\!C_{12} {}^1\!H_{22}{}^{16}\!O_{11}</math>. The molecular mass is

<math>12\times 12+1\times22+16\times11=342</math> daltons.

1 mole of the sugar = <math> (1\ mole)\times \left(\frac{6.02\times10^{23}\ molecules}{1 mole}\right)\times\left(\frac{342\ daltons}{1\ molecules}\right)\times\left(\frac{1 gram}{6.02\times10^{23}\ daltons}\right)=342</math> grams. As one sees, the molecular mass and molar mass are equal except that their units are daltons and grams, respectively.

Note: A dalton is also known as an atomic mass unit (AMU).