Molecular Weight
Definition and meaning of Molecular Weight in chemistry.
Molecular weight is the mass of a given molecule, typically measured in atomic mass units (amu) or daltons (Da). It is calculated as the sum of the atomic weights of all the atoms present in the molecular formula.
In more detail
While the term molecular weight is widely used in chemistry, the more accurate term is molecular mass. It is a crucial parameter in stoichiometry for determining the mass of a substance needed for a chemical reaction or preparing solutions of specific concentrations. To find the molar mass of a substance in grams per mole, which is numerically equivalent to the molecular weight, one simply adds the standard atomic weights of the constituent elements. This fundamental property allows chemists to relate the microscopic mass of individual molecules to the macroscopic quantities measured in a laboratory setting.
Key facts
| Field | General Chemistry |
|---|---|
| Units | amu or g/mol |
| Alternate name | Molecular mass |
The molecular weight of carbon dioxide (CO2) is approximately 44.01 amu, calculated by adding the atomic weight of one carbon atom and two oxygen atoms.
Frequently asked questions
Is molecular weight the same as molar mass?
They are numerically identical, but molecular weight is the mass of one molecule in amu, while molar mass is the mass of one mole of molecules in grams per mole.