Question

Why is the molecular formula of a compound more useful to a forensic scientist than an empirical formula?

Answer 1

An empirical formula can represent more than one compound. A molecular formula represents one compound, and its structural isomers if applicable.

Explanation:

Examples:
Molecular compounds with empirical formula `"CH"`:
acetylene: `"C"_2"H"_2"`
benzene: `"C"_6"H"_6"`

Molecular compounds with empirical formula `"CH"_2"`:
ethylene: `"C"_2"H"_4"`
butene: `"C"_4"H"_8"`
cyclohexane: `"C"_6"H"_12"`

Molecular compounds with empirical formula `"CH"_2"O"`:
formaldehyde: `"CH"_2"O"`
acetic acid: `"C"_2"H"_4"O"_2"`
glyceraldehyde: `"C"_3"H"_6"O"_3"`
glucose, fructose, galactose (structural isomers): `"C"_6"H"_12"O"_6"`

http://www.chem.wisc.edu/deptfiles/genchem/sstutorial/Text6/Tx65/tx65.html