The correct option is **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 when dissolved in water, and their reactivity with bases. 2. **Why Option B is Correct:** - One of the classic tests for acids is their effect on 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. The litmus paper is sensitive to these changes in pH, and the red color indicates an acidic environment (pH < 7). 3. **Why the Other Options are Incorrect:** - **Option A: Acids have a bitter taste and slippery feel.** - This statement is incorrect because it describes the characteristics of bases, not acids. Bases typically have a bitter taste and a slippery feel due to their ability to react with fats and oils, forming soap-like substances. Acids, on the other hand, are known for their sour taste (like vinegar or lemon juice) and do not have a slippery feel. - **Option C: Acids produce hydroxide ions (OH⁻) in solution.** - This statement is incorrect because it describes the behavior of bases, not acids. Acids produce hydrogen ions (H⁺) when dissolved in water. In contrast, bases produce hydroxide ions (OH⁻). For example, sodium hydroxide (NaOH) is a base that dissociates in water to produce Na⁺ and OH⁻ ions. - **Option D: Acids are generally insoluble in water.** - This statement is misleading. While some acids are indeed insoluble in water (like certain organic acids), many common acids, such as hydrochloric acid (HCl) and sulfuric acid (H₂SO₄), are highly soluble in water. The solubility of an acid depends on its chemical structure and the nature of its interactions with water molecules. ### Summary of Key Points: - Acids turn blue litmus paper red, indicating their acidic nature. - Acids are characterized by a sour taste and the ability to donate protons (H⁺). - Bases, not acids, have a bitter taste and slippery feel, and they produce hydroxide ions (OH⁻). - Many common acids are soluble in water, contrary to the claim that acids are generally insoluble. This understanding of acids and their properties is crucial for recognizing their behavior in chemical reactions and their role in various applications in chemistry.