**Correct Option: B. It completely dissociates into its ions, resulting in a high concentration of hydrogen ions.** ### Detailed Explanation: 1. **Understanding Strong Acids:** - A strong acid is defined as an acid that completely dissociates in water. This means that when a strong acid is added to water, it breaks apart entirely into its constituent ions. For example, hydrochloric acid (HCl) dissociates into hydrogen ions (H⁺) and chloride ions (Cl⁻) when dissolved in water: \[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \] - This complete dissociation leads to a high concentration of hydrogen ions in the solution, which is responsible for the acidic properties of the solution. 2. **Why Option B is Correct:** - Since strong acids dissociate completely, the concentration of hydrogen ions (H⁺) in the solution is directly related to the concentration of the acid itself. For example, a 1 M solution of HCl will produce a 1 M concentration of H⁺ ions. - The high concentration of H⁺ ions is what makes the solution strongly acidic, resulting in a low pH (typically below 3 for strong acids). 3. **Why the Other Options are Incorrect:** - **Option A: It partially ionizes, producing a low concentration of hydrogen ions.** - This statement describes weak acids, not strong acids. Weak acids only partially dissociate in water, resulting in a lower concentration of hydrogen ions. For example, acetic acid (CH₃COOH) is a weak acid that does not fully ionize, leading to a lower concentration of H⁺ ions compared to a strong acid at the same concentration. - **Option C: It undergoes a reversible reaction with water, establishing an equilibrium.** - This statement is also characteristic of weak acids. Strong acids do not establish an equilibrium with water; they fully dissociate. In contrast, weak acids establish an equilibrium between the undissociated acid and its ions, which can be represented as: \[ \text{HA} \rightleftharpoons \text{H}^+ + \text{A}^- \] where HA is the weak acid. Strong acids do not have this reversible reaction because they do not remain in the undissociated form in solution. - **Option D: It produces hydroxide ions when dissolved in water.** - This statement is incorrect for strong acids. Strong acids produce hydrogen ions (H⁺) when dissolved in water, not hydroxide ions (OH⁻). In fact, the presence of H⁺ ions in solution leads to a decrease in the concentration of OH⁻ ions, as the product of the concentrations of H⁺ and OH⁻ ions in water is constant at 25°C (Kw = 1.0 x 10⁻¹⁴). Therefore, adding a strong acid will lower the pH and increase the concentration of H⁺, not OH⁻. ### Summary: - Strong acids completely dissociate in water, resulting in a high concentration of hydrogen ions (H⁺). - Weak acids only partially ionize, leading to lower concentrations of H⁺ and establishing an equilibrium. - Strong acids do not produce hydroxide ions; they increase the acidity of the solution by increasing H⁺ concentration. - Understanding the behavior of acids in water is crucial for predicting their effects on pH and chemical reactions. ### Revision Summary: - Strong acids fully dissociate in water, producing high concentrations of H⁺ ions. - Weak acids partially ionize, resulting in lower H⁺ concentrations and establishing equilibrium. - Strong acids do not produce hydroxide ions; they lower pH by increasing H⁺ concentration. - Familiarity with acid behavior is essential for understanding acid-base chemistry and pH calculations.