* Empirical Formula: The empirical formula represents the simplest whole-number ratio of atoms in a compound. CH2O is already in its simplest whole-number ratio, so it's the empirical formula.

* Molecular Formula: The molecular formula shows the actual number of atoms of each element in a molecule. CH2O also represents the actual number of atoms in a molecule of formaldehyde.

In this case, the empirical formula and molecular formula are the same because the simplest ratio of atoms is also the actual composition of the molecule.