relative molecular mass The ratio of the average mass per molecule or specified entity of a substance to 1/12 of the mass of a carbon-12 atom. Also called molecular weight and represented by the symbol Mr, relative molecular mass is equal to the sum of the relative atomic masses of all the atoms that comprise a molecule. Related category PHYSICAL CHEMISTRY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |