theory of indicators
Học thuậtThân thiện
Definition
Noun: - (Chemistry): A theory stating that all acid-base indicators are themselves either weak acids or weak bases. The key principle is that the ionized (dissociated) form of the indicator molecule has a different color than its non-ionized (undissociated) form. The color change observed during titration is due to a shift in the equilibrium between these two forms as the pH of the solution changes.
Usage Examples
- Noun:
- Understanding the theory of indicators is essential for choosing the correct indicator for an acid-base titration.
- According to the theory of indicators, phenolphthalein is colorless in its acidic (non-ionized) form and pink in its basic (ionized) form.
- The experiment demonstrated the theory of indicators by showing how the color of methyl orange shifts from red to yellow as the solution becomes more basic.
Advanced Usage
- "Application of the theory of indicators": Refers to the practical use of this theory in analytical chemistry to determine titration endpoints.
- The accurate determination of the equivalence point relies on the proper application of the theory of indicators.
Variants and Related Words
- Acid-base indicator (n): A substance that changes color depending on the pH of the solution it is in, operating on the principles described by the theory of indicators.
- Litmus paper is a common acid-base indicator.
- Transition range (n): The narrow pH interval over which an indicator changes color, a concept explained by the theory of indicators.
- An indicator's transition range should match the pH change at the equivalence point.
Synonyms
- Ostwald's theory of indicators: A specific name for this theory, attributed to the physical chemist Wilhelm Ostwald.
- Ostwald's theory of indicators provides a quantitative explanation for the color change.
Noun
- (chemistry) the theory that all indicators are either weak acids or weak bases in which the color of the ionized form is different from the color before dissociation