In this video
Molecuar Mass(M):-
Molecuar mass is the sum of atomic masses of the elements present in a molecule.It is calculated by adding the atomic mass of all the atoms present in one molecule of the compound.
example :-The average mass of one Molecule of a compound in atomic mass unit is called
molecuar mass(M).
Hence

Molecuar mass (M)=Mr× 1u=Mru

Calculate molecular weight of Aluminium hydroxide|Molar mass of Al(OH)3|Al(OH)3 Molar mass