a) Define atomic mass unit.
b) Distinguish between molecular mass and molar mass.
c) Give an example of (i) diatomic, (ii) triatomic molecule of compounds.

(a) Atomic mass unit is the unit of mass used to express atomic and molecular weights, equal to 1/12th of the mass of an atom of carbon-12.

(b) Molecular mass refers to the mass of a molecule, while molar mass refers to the mass of a mole of a substance.

(c) Nitrogen, $N_2$, is a diatomic compound. Ozone, $O_3$, is a triatomic compound.