**Correct Option: B. Acids increase the concentration of hydrogen ions (H+) in solution.** ### Detailed Explanation: 1. **Understanding Acids:** - Acids are substances that, when dissolved in water, increase the concentration of hydrogen ions (H+). This is a fundamental property of acids and is central to the Brønsted-Lowry definition of acids, which states that an acid is a proton donor. 2. **Behavior in Aqueous Solution:** - When an acid, such as hydrochloric acid (HCl), is added to water, it dissociates into its ions: \[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \] - The release of H+ ions into the solution increases the overall concentration of hydrogen ions, which is what characterizes an acidic solution. 3. **pH Scale:** - The pH scale measures the acidity or basicity of a solution. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic (alkaline) solution. Since acids increase H+ concentration, they naturally lead to a lower pH. ### Why Other Options Are Incorrect: - **Option A: Acids release hydroxide ions (OH-) when dissolved in water.** - This statement is incorrect because it describes the behavior of bases, not acids. Bases release hydroxide ions (OH-) in solution, which decreases the concentration of H+ ions and raises the pH. - **Option C: Acids are characterized by a slippery feel when in solution.** - This statement is misleading. While bases (like soap) are known for their slippery feel due to the formation of soap-like compounds, acids do not have this characteristic. In fact, many acids can be corrosive and do not feel slippery. - **Option D: Acids have a pH greater than 7.** - This statement is incorrect. Acids have a pH less than 7. A pH greater than 7 indicates a basic solution. Therefore, this option contradicts the fundamental definition of acids. ### Summary of Key Points: - Acids increase the concentration of hydrogen ions (H+) in solution, which is the defining characteristic of acids. - The pH of an acidic solution is less than 7, while basic solutions have a pH greater than 7. - Acids do not release hydroxide ions; that is a property of bases. - Acids do not have a slippery feel; this is a characteristic of basic solutions. By understanding these concepts, you can better grasp the behavior of acids in aqueous solutions and differentiate them from bases.