Molecular weight (also known as molecular mass) is the total weight of all the atoms in a molecule. It’s calculated by adding up the atomic weights of each atom present in the molecule.
The unit used for molecular weight is called the Dalton (Da) or atomic mass unit (amu). For example:
To calculate the molecular weight of a molecule:
A molecular weight chart provides the weights of commonly used molecules. Here are a few examples:
To make calculations easier, you can use a molecular weight calculator. These tools are available online and allow you to enter a chemical formula, automatically giving you the molecular weight. Simply type the formula (e.g., H₂O) into the calculator and get the result instantly.
The molecular weight of any specific compound is equal to the sum of the atomic weights of all the atoms that make up the molecule.
The total atomic weights of all the atoms included in the empirical formula of a given molecule are the formula weight of that molecule. The molecular weight of a molecule, on the other hand, is the total atomic weight of all the atoms according to the molecular formula.
The molecular weight is commonly measured in amu or Da. The terms amu and Da refer to the atomic mass unit and the atomic mass unit, respectively.