Question

define molecular mass and relative formula unit mass .
In at least 20 word each

Answer 1

molecular mass of substance is the average relative mass of its molecules as compared with that of an atomC-12 isotope .
molecular mass of a substance represents the number of times the molecule of that substance

Answer 2

MOLECULAR MASS is the sum of atomic masses of all the atoms present in a molecules of a substance
RELATIVE ATOMIC MASSES the average atomic mass of the atoms as compared to 1/12th the mass of one of 12th atom