Formaldehyde and acetic acid have the same empirical formula but different molecular formulas and molecular weights.

Here's a breakdown:

* Empirical formula: The simplest whole-number ratio of atoms in a compound. Both formaldehyde and acetic acid have the empirical formula CH₂O.

* Molecular formula: The actual number of atoms of each element in a molecule.

* Formaldehyde: CH₂O (one carbon, two hydrogen, one oxygen)

* Acetic acid: C₂H₄O₂ (two carbon, four hydrogen, two oxygen)

* Molecular weight: The sum of the atomic weights of all atoms in a molecule.

* Formaldehyde: 30 g/mol

* Acetic acid: 60 g/mol

In summary:

While formaldehyde and acetic acid share the same empirical formula (CH₂O), they differ in their molecular formulas and molecular weights. This difference arises from the different arrangements of atoms within their molecules.