The molecular weight of a molecule is the sum of the atomic weights of the elements that constitute the molecule. Essentially, molecular mass or molecular weight is the mass of a molecule.
Example 1: Molecular weight of water (H2O)
|2 Hydrogen atoms||2 X 1||2|
|1 Oxygen atom||1 X 16||16|
|Molecular weight of H2O||18|
Example 2: Molecular weight of sodium bicarbonate (NaHCO3):
|1 Sodium atom||1 X 23||23|
|1 Hydrogen atom||1 X 1||1|
|1 Carbon atom||1 X 12||12|
|3 Oxygen atoms||3 X 16||48|
|Molecular weight of NaHCO3||84|
Molecular weight, like atomic weight, is expressed simply as a figure without a unit.