What type of substances ionize in solution to produce H ions?

The correct answer is the substances that ionize in solution to produce hydrogen ions (H⁺) are acids. Acids, when dissolved in water, dissociate to release H⁺ ions, which is a defining characteristic of acidic substances. This release of hydrogen ions is what contributes to the acidity of a solution, and it is why acids are known to have a sour taste and can lower the pH of a solution.

In contrast, neutral substances do not produce H⁺ or hydroxide (OH⁻) ions when dissolved in water, maintaining a neutral pH. Bases are substances that, when dissolved in water, produce hydroxide ions (OH⁻) rather than hydrogen ions. Salts can dissociate into cations and anions when dissolved in water, but they do not inherently release H⁺ ions, instead providing a combination of ions that can result from acid-base reactions.

Understanding the role of acids in generating H⁺ ions is fundamental in chemistry, especially in the context of acid-base reactions and pH levels in various solutions.