chemistry question!!!!!!!!!!!

molecular mass(molecular weight)=the sum of the atomic masses of the molesules.
e.g. Na2CO3
molecular mass=2*22.99+12.01+3*16.00=106.0

Relative molecular mass is used to describe the relative masses of molecules.

Relative molecular mass of an element or compound
= Sum of relative atomic masses of all atoms present in one molecule of the element or compound