Which statement best describes the difference between an empirical formula and a molecular formula?

• A. An empirical formula always contains more atoms than a molecular formula.
• B. A molecular formula is used only for ionic compounds, while an empirical formula is used for covalent compounds.
• C. An empirical formula shows the simplest whole-number ratio of atoms in a compound, while a molecular formula shows the actual number of atoms of each element in a molecule.
• D. An empirical formula and a molecular formula are always identical for all compounds.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand that the empirical formula represents the simplest whole-number ratio of atoms of each element in a compound. It does not necessarily show the actual number of atoms present in a molecule, but rather the relative proportions.
2. Step 2: Recognize that the molecular formula shows the actual number of atoms of each element in a single molecule of the compound. This means it can be a multiple of the empirical formula.
3. Step 3: Note that the empirical formula is useful for both ionic and covalent compounds because it reflects the simplest ratio of ions or atoms, while the molecular formula specifically applies to molecular (covalent) compounds where discrete molecules exist.
4. Step 4: Understand that the empirical formula can sometimes be the same as the molecular formula if the molecule's composition is already in the simplest ratio, but this is not always the case.
5. Step 5: Conclude that the key difference is that the empirical formula shows the simplest ratio, whereas the molecular formula shows the exact number of atoms in a molecule, making the correct description: 'An empirical formula shows the simplest whole-number ratio of atoms in a compound, while a molecular formula shows the actual number of atoms of each element in a molecule.'