Empirical formula from molecular formula of ethanoic acid

Steps:

• Recall the molecular formula of ethanoic acid (CH₃COOH) is C₂H₄O₂.
• Count atoms: 2 carbon, 4 hydrogen, 2 oxygen.
• Divide subscripts by greatest common divisor (2): C₁H₂O₁.
• Write as simplest ratio: CH₂O.

Why A is correct:

• CH₂O represents the lowest whole-number ratio of atoms in C₂H₄O₂, per the definition of empirical formula.

Why the others are wrong:

• B (CH₃O): Incorrect H:C ratio (3:1 vs. 2:1 in acid).
• C (CH₂O₂): Excess oxygen (2:1 O:C vs. 1:1).
• D (CH₃O₂): Wrong H:C (3:1) and excess oxygen (2:1 O:C).

Final answer: A