What is the definition of molecule mass?

The correct definition of molecular mass is the sum of the compound's atomic masses. Molecular mass refers to the combined total mass of all the atoms present within a molecule, which is calculated by adding the atomic masses (usually represented in atomic mass units, or amu) of each atom that constitutes the molecule. This value provides important information about the molecule's properties and behavior in chemical reactions.

In the context of chemistry, understanding molecular mass is crucial when performing calculations involving moles, reactions, and stoichiometric conversions, as it allows for determining how much of a substance is present or needed in a reaction. Each atom contributes to the overall molecular mass based on its specific atomic mass, which represents the average mass of that element's isotopes weighted by their natural abundance.