Question

The formula unit mass of a substance is the:
A) Sum of atomic masses of all atoms in a formula unit of a compound.
B) Relative atomic masses of the atoms.
C) Equal to the numerical value of the atomic mass.
D) None of the above

Answer 1

The answer is based upon the fact that mass of substance is internal property of substance and the total mass of all the atoms constitutes the mass of the object and mass of one atom of the substance constitutes unit mass.

Complete answer:
We have studied in our chemistry classes about the atoms and its structure along with its constituents and also the composition and also several parameters that are associated with it.
We shall see what the formula unit mass of substance is by considering the general aspects of the atom.
- The atom is the smallest quantity that constitutes a molecule when combined together.
- Atoms are composed of central nuclei which have protons that are positively charged and neutrons that are neutral and around the nucleus there is an orbit in which a negatively charged particle called electrons revolves.
- The number of protons in the nucleus of an atom is always equal to the number of electrons that are revolving around them.
- More than two such types of atoms combine together to form compounds and therefore, the unit mass will be equal to the sum of the atomic masses of all atoms in a formula unit of the compound.

Thus, the correct answer is option A)

Note: Do not be confused about the relative atomic mass and formula unit mass relative atomic mass is fraction of average mass of one atom of the element to that of one twelfth mass of carbon – 12 atoms and formula unit mass is the sum of atomic masses of all atoms in a formula unit of compound.