which statement best relates an empirical formula with a molecular formula?\no they are always different for…

Brief Explanations:

The empirical formula is the simplest whole - number ratio of atoms in a compound, and the molecular formula is a multiple of the empirical formula. So, molecular formulas can be determined from empirical formulas when the molar mass of the compound is known. The first option is incorrect as they can be the same (e.g., for $\text{H}_2\text{O}$). The second option is wrong because empirical formulas are already in the simplest form. The fourth option is incorrect since only the molecular formula shows the actual number of atoms of each element in a compound, while the empirical formula shows the simplest ratio.

Answer:

C. Molecular formulas can be determined from empirical formulas.