1. Arrhenius Definition: This definition is simple and focuses on the behavior of acids in water. An Arrhenius acid is a substance that increases the concentration of hydrogen ions (H⁺) when dissolved in water.
* Example: Hydrochloric acid (HCl) in water dissociates into H⁺ and Cl⁻ ions, increasing the H⁺ concentration.
2. Brønsted-Lowry Definition: This is a more general definition that encompasses a wider range of substances. A Brønsted-Lowry acid is a substance that can donate a proton (H⁺) to another substance.
* Example: Hydrochloric acid (HCl) donates a proton to water (H₂O), forming hydronium ions (H₃O⁺) and chloride ions (Cl⁻).
Key Points to Remember:
* Acids are generally sour-tasting and can react with bases to form salts and water.
* Acids can corrode metals and turn litmus paper red.
* The strength of an acid is determined by its ability to donate protons.
Which definition is "best" depends on the specific context and level of detail required. For basic understanding, the Arrhenius definition is sufficient. However, the Brønsted-Lowry definition provides a more comprehensive and general understanding of acid behavior.