Question

Define molecular unit mass.

Answer 1

the molar mass M is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol.

Answer 2

Relative molecular mass or molecular weight is the mass of a molecule. It is calculated as the sum of the relative atomic masses of each constituent element multiplied by the number of atoms of that element in the molecular formula.

The unit, equivalent to 1/12 the mass of a carbon-12 atom, is properly called the unified atomic mass unit (often, but obsoletely, just “atomic mass unit”) or the Dalton (Da), after John Dalton, of course.