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Mass of a molecule of a substance, based on 12 as the atomic weight of carbon-12. It is calculated in practice by summing the atomic weights of the atoms making up the substance's molecular formula. The molecular weight of a hydrogen molecule (chemical formula H) is 2 (after rounding off); for many complex organic molecules (e.g., proteins, polymers) it may be in the millions.
Variants of MOLECULAR WEIGHT
molecular weight also called molecular mass
This entry comes from Encyclopædia Britannica Concise. For the full entry on molecular weight, visit Britannica.com.