Read Orthocresol's answer here first: What is the difference between "molecular mass", "average atomic mass" and "molar mass"?

Orthocresol, in his answer, says that atomic mass is the weighted average mass of the atoms of an element and molecular mass is the mass of the molecule of an element/ compound obtained by adding the atomic masses of the constituent element's/ elements' atoms. Both atomic mass and molecular mass have the units of mass which may be kilograms, grams, daltons or a.m.u.

Relative atomic mass/ atomic weight is the ratio between the atomic mass of an atom and 1/12th of the atomic mass of a C-12 atom and similarly, relative molecular mass/molecular weight is the ratio of the molecular mass of a molecule and 1/12th of the atomic mass of a C-12 atom. Both R.A.M. and R.M.M are unitless since they are the ratio of two physical quantities which have the units of mass.

My Question: Atomic masses and molecular masses expressed in a.m.u or u have the same numerical value as R.A.M. and R.M.M respectively. What is the point of having R.A.M and R.M.M?



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