Molar Mass
Definition and meaning of Molar Mass in chemistry.
Molar mass is the physical mass of a given substance divided by the exact amount of that substance, typically expressed in standard units of grams per mole (g/mol). It represents the specific mass of one mole, or Avogadro's number, of representative particles of that chemical substance.
In more detail
The molar mass of an element is numerically equal to its standard atomic weight on the periodic table. For a chemical compound, the molar mass is calculated by adding the standard atomic weights of all the individual atoms present in its chemical formula. This property serves as a crucial conversion factor in stoichiometry, allowing chemists to accurately translate between the measurable mass of a physical sample and the exact number of moles it contains. It bridges the critical gap between the macroscopic laboratory scale and the microscopic atomic scale.
Key facts
| Field | General Chemistry |
|---|---|
| Standard Unit | g/mol |
| Mathematical Relation | Total Mass / Number of Moles |
The molar mass of pure water (H2O) is approximately 18.015 g/mol, calculated by adding the mass of two hydrogen atoms and one oxygen atom.
Frequently asked questions
Is molar mass the exact same thing as molecular weight?
They are numerically the same but have different units. Molecular weight is dimensionless or measured in atomic mass units (amu), while molar mass is strictly in g/mol.