Theories of acid-base indicators
Acid-base indicators are substances that change color depending on the acidity or basicity of a solution. There are several theories that explain how acid-base indicators work, including the Arrhenius theory, the Brønsted-Lowry theory, and the Lewis theory.
- Arrhenius Theory: This theory, proposed by Swedish chemist Svante Arrhenius in 1884, defines an acid as a substance that produces hydrogen ions (H+) in solution, and a base as a substance that produces hydroxide ions (OH-) in solution. According to this theory, acid-base indicators are substances that change color when there is a change in the concentration of H+ or OH- ions in solution.
- Brønsted-Lowry Theory: This theory, proposed by Danish chemist Johannes Brønsted and English chemist Thomas Lowry in 1923, defines an acid as a substance that donates a proton (H+) in a chemical reaction, and a base as a substance that accepts a proton. According to this theory, acid-base indicators are substances that can be either weak acids or weak bases, and they change color when they undergo a protonation or deprotonation reaction.
- Lewis Theory: This theory, proposed by American chemist Gilbert Lewis in 1923, defines an acid as a substance that accepts a pair of electrons, and a base as a substance that donates a pair of electrons. According to this theory, acid-base indicators are substances that can act as Lewis acids or Lewis bases, and they change color when they undergo a reaction that involves the transfer of electrons.
Overall, these theories help explain how acid-base indicators work by describing the chemical properties of acids and bases and their interactions with other substances.
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