which statement best relates an empirical formula with a molecular formula? they are always different for…

Brief Explanations:

The empirical formula gives the simplest whole - number ratio of elements in a compound. The molecular formula is a multiple of the empirical formula ($Molecular\ formula=(Empirical\ formula)_n$, where $n$ is a positive integer). So, molecular formulas can be determined from empirical formulas if the molar mass of the compound is known to find the value of $n$. The first option is incorrect as they can be the same (when $n = 1$). The second option is a characteristic of empirical formulas themselves, not a relation to molecular formulas. The fourth option is wrong because only the molecular formula shows the actual ratio of elements in the compound's molecule, while the empirical formula shows the simplest ratio.

Answer:

Molecular formulas can be determined from empirical formulas.