The correct option is **B. Acids react with metals to produce hydrogen gas.** ### Detailed Explanation: 1. **Understanding Acids:** - Acids are substances that can donate protons (H⁺ ions) in a solution. They typically have a sour taste, can conduct electricity, and have a pH less than 7. Common examples include hydrochloric acid (HCl) and sulfuric acid (H₂SO₄). 2. **Why Option B is Correct:** - One of the classic reactions of acids is their ability to react with certain metals. When an acid reacts with a reactive metal (like zinc, magnesium, or aluminum), it produces hydrogen gas and a salt. The general reaction can be represented as: \[ \text{Acid} + \text{Metal} \rightarrow \text{Salt} + \text{Hydrogen gas (H₂)} \] - For example, when hydrochloric acid reacts with zinc: \[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl₂} + \text{H₂} \] - This reaction is significant because the evolution of hydrogen gas can be observed as bubbles forming in the solution, which is a clear indicator of the reaction taking place. 3. **Why the Other Options are Incorrect:** - **Option A: Acids have a slippery feel and can taste bitter.** - This statement is incorrect because acids do not have a slippery feel; that property is characteristic of bases. Bases feel slippery due to their ability to react with oils and fats, forming soap-like substances. Additionally, acids typically have a sour taste, not a bitter one. Bitter tastes are associated with bases. - **Option C: Acids have a pH greater than 7.** - This statement is incorrect. Acids have a pH less than 7. The pH scale ranges from 0 to 14, where values below 7 indicate acidity, values of 7 indicate neutrality (pure water), and values above 7 indicate basicity (alkalinity). Therefore, this option misrepresents the fundamental property of acids. - **Option D: Acids turn litmus paper blue.** - This statement is also incorrect. Acids turn blue litmus paper red. Litmus paper is a common pH indicator used to test the acidity or basicity of a solution. When an acid is present, it donates protons, which causes the blue litmus to change color to red, indicating an acidic environment. ### Summary of Key Points: - Acids react with metals to produce hydrogen gas, which is a defining characteristic of their behavior. - Acids have a pH less than 7 and taste sour, not bitter. - Acids turn blue litmus paper red, not the other way around. - Understanding the properties of acids is crucial for predicting their reactions and behaviors in various chemical contexts. This thorough understanding of acids and their properties will help you in both theoretical and practical aspects of chemistry.