Answer: (a) CH3COOH; (b) vinegar is used to preserve pickles and food.
(a) Acetic acid is CH3COOH (ethanoic acid); its structural formula is CH3–COOH.
(b) Vinegar is a 4–8% solution of acetic acid in water. It is used as a preservative for pickles, sauces and other food, and as a flavouring agent and household cleaning agent.