Final answer:
The molecular formula of naphthalene is C10H8, which is determined by finding the multiple of its empirical formula C5H4 that matches its molar mass of 128.16 g/mol.
Step-by-step explanation:
The molecular formula of a compound represents the actual number of atoms of each element in one molecule of the compound. To determine the molecular formula of naphthalene, which has an empirical formula of C5H4 and a molar mass of 128.16 g/mol, we first calculate the molar mass of the empirical formula. In this case, the molar mass of C5H4 is 5(12.01 g/mol) for carbon + 4(1.008 g/mol) for hydrogen, which equals 64.08 g/mol. This means that the molecular formula must be a multiple of the empirical formula.
To find this multiple, we divide the given molar mass of naphthalene, 128.16 g/mol, by the molar mass of the empirical unit, 64.08 g/mol, getting a result of approximately 2. Therefore, to get the molecular formula, we multiply the subscripts in the empirical formula by this number, leading to C10H8. So, the molecular formula of naphthalene is C10H8.