Question

What is the difference between molecular mass and formula unit mass?
A. Molecular mass is for molecules , and formula mass is for ionic compounds.
B. Molecular mass is for ionic compounds, and formula mass is for molecules.
C. Both are exactly the same.
D. None of the above

Answer 1

Hint: Molecular mass is a term for the average relative mass of a single molecule and formula mass is a term used for the sum of the atomic mass of constituents atoms.

Complete answer:
Molecular mass is the sum of the atomic masses of the atoms in a molecule means it gives the mass of a molecule. Molecular mass is also known as molecular weight and it actually gives the mass of a molecule relative to that of a carbon twelve atom which has a mass of twelve units.
Formula mass of a substance is actually the sum of atomic masses of constituents atoms in an ionic compound or we can say that the sum of atomic masses of the ions present in the formula unit of an ionic compound.
Molecular mass and formula mass are somewhat the same terms but we use it differently because molecules are actually covalent compounds means they have only non metals and an ionic compound cannot be a molecule therefore we just simply say formula mass when we are taking ionic compounds.
Hence the correct option is A which means molecular mass is for molecules and formula mass is for ionic compounds.

Note: Molecular mass is for covalent compounds means compounds that contain only non metals while formula mass is for ionic compounds means compounds that contain metals and non metals.