Definitions and Core Differences
In chemistry, acids are substances that donate hydrogen ions (H⁺) in aqueous solutions, while bases accept hydrogen ions or donate hydroxide ions (OH⁻). Acids typically have a pH below 7, making them sour and corrosive, whereas bases have a pH above 7, often feeling slippery and bitter. This distinction arises from the Arrhenius theory, where acids increase H⁺ concentration and bases increase OH⁻ concentration in water.
Key Properties and Behaviors
Acids react with metals to produce hydrogen gas and turn blue litmus paper red, while bases neutralize acids to form salts and water, turning red litmus paper blue. According to the Brønsted-Lowry theory, acids are proton donors and bases are proton acceptors. Common acids include hydrochloric acid (HCl), and bases include sodium hydroxide (NaOH). Strength is determined by dissociation degree: strong acids/bases fully ionize, while weak ones partially do.
Practical Example: Reaction with Indicators
Consider vinegar (acetic acid, a weak acid) and baking soda solution (sodium bicarbonate, a base). When blue litmus paper is dipped in vinegar, it turns red, indicating acidity. In the baking soda solution, the paper turns blue, showing basicity. Mixing them produces carbon dioxide gas, demonstrating neutralization: CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂.
Importance and Real-World Applications
Understanding acid-base differences is crucial for pH regulation in biological systems, such as blood buffering against pH changes to maintain homeostasis. In industry, acids are used in fertilizers and batteries, while bases appear in soaps and antacids. This knowledge prevents misconceptions like assuming all acids are harmful—many, like citric acid in fruits, are safe—and aids in safe handling and environmental management.