Define the term relative molecular mass? ?

Relative molecular mass is the average mass of a molecule of a substance compared to the mass of a carbon-12 atom, which is assigned a mass of exactly 12 atomic mass units. It is calculated by adding up the atomic masses of all the atoms in a molecule.

Relative molecular mass (Mr) is the dimensionless ratio of the average mass of a molecule of a given substance to 1/12 of the mass of an atom of carbon-12. It is a measure of how heavy a molecule is compared to the carbon-12 atom.

The relative molecular mass of a molecule is the sum of the relative atomic masses of the atoms in the molecule. For example, the relative molecular mass of water (H2O) is 18, which is the sum of the relative atomic masses of two hydrogen atoms (1 each) and one oxygen atom (16).

Relative molecular mass is also known as molecular weight, molecular mass, or formula weight.