Which molecular formula is also an empirical formula?

• A. $C_2{H}_5\mathrm{Cl}$
• B. $N_2{O}_4$
• C. $H_2{O}_2$
• D. $C_6{H}_{12}{O}_6$

Answer: (A)

Verified step by step guidance

1. Understand that an empirical formula represents 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.
2. For each given molecular formula, determine the ratio of atoms by dividing the subscripts of each element by their greatest common divisor (GCD).
3. Check if the molecular formula is already in its simplest form by seeing if the GCD of all subscripts is 1; if so, the molecular formula is also the empirical formula.
4. Apply this to each formula: for example, for C2H5Cl, the subscripts are 2, 5, and 1 (implied for Cl), and the GCD is 1, so it is already the simplest ratio.
5. Compare all formulas this way and identify which one has no smaller whole-number ratio, confirming it is both the molecular and empirical formula.