Which one of the following best defines an acid? A. an aqueous solution with a pH of less than 7.0 B. a substance that reacts with water to produce hydrogen ions C. a substance that reacts with water to produce hydroxide ions D. a substance that reacts with water to produce hydronium ions
Option D. A substance that reacts with water to produce hydronium ions is defines an acid. A “hydrogen ion” H is a bare proton which, is freely exists, might connect to a water molecule to form the hydronium ion (H3O ). So choice D is a better solution than Choice B.
