Molar Mass - Measurement

Measurement

Molar masses are almost never measured directly. They may be calculated from standard atomic masses, and are often listed in chemical catalogues and on material safety data sheets (MSDS). Molar masses typically vary between:

1–238 g/mol for atoms of naturally-occurring elements;

10–1000 g/mol for simple chemical compounds;

1000–5,000,000 g/mol for polymers, proteins, DNA fragments, etc.

While molar masses are almost always, in practice, calculated from atomic weights, they can also be measured in certain cases. Such measurements are much less precise than modern mass spectrometric measurements of atomic weights and molecular masses, and are of mostly historical interest. All of the procedures rely on colligative properties, and any dissociation of the compound must be taken into account.