**Correct Option: B. Acids turn blue litmus paper red.** ### Detailed Explanation: 1. **Understanding Acids:** - Acids are substances that can donate protons (H⁺ ions) in a solution. They are characterized by their sour taste, ability to conduct electricity, and their reactivity with bases to form salts and water. 2. **Why Option B is Correct:** - One of the classic tests for identifying acids is the use of litmus paper, which is a pH indicator. When blue litmus paper is exposed to an acidic solution, it changes color to red. This color change occurs because the acid donates protons to the water, increasing the concentration of H⁺ ions in the solution, which lowers the pH below 7. The red color indicates an acidic environment. 3. **Why the Other Options are Incorrect:** - **Option A: Acids have a bitter taste and feel slippery to the touch.** - This statement is incorrect because it describes the properties of bases, not acids. Bases typically have a bitter taste and feel slippery due to the presence of hydroxide ions (OH⁻). Acids, on the other hand, are known for their sour taste and do not feel slippery. - **Option C: Acids produce hydroxide ions (OH⁻) when dissolved in water.** - This statement is incorrect. Acids do not produce hydroxide ions; instead, they produce hydrogen ions (H⁺) when dissolved in water. It is bases that produce hydroxide ions in solution. For example, when hydrochloric acid (HCl) dissolves in water, it dissociates into H⁺ and Cl⁻ ions, not OH⁻ ions. - **Option D: Acids have a pH greater than 7.** - This statement is also incorrect. The pH scale ranges from 0 to 14, where a pH of 7 is neutral (pure water). Acids have a pH less than 7. A pH greater than 7 indicates a basic (alkaline) solution, which is the opposite of acidic. ### Summary of Key Points: - Acids turn blue litmus paper red due to the increase in H⁺ ions in solution. - Acids are characterized by a sour taste and do not feel slippery. - Acids produce H⁺ ions, not OH⁻ ions, when dissolved in water. - Acids have a pH less than 7, while bases have a pH greater than 7. ### Revision Summary: - Acids turn blue litmus paper red. - Acids taste sour and do not feel slippery. - Acids produce H⁺ ions in solution. - Acids have a pH less than 7.