pHmérkkel

pHmérkkel is a term used in chemistry to describe a substance that changes color in response to variations in pH. These substances are typically weak acids or bases, and their color change is due to a reversible chemical reaction. When the pH of a solution changes, the equilibrium of this reaction shifts, leading to a change in the molecule's structure and thus its color.

Common examples of pHmérkkel include litmus, phenolphthalein, and methyl orange. Litmus, for instance, is a mixture of different organic dyes that turns red in acidic solutions and blue in alkaline solutions. Phenolphthalein is colorless in acidic conditions but becomes pink or fuchsia in alkaline solutions above a certain pH. Methyl orange exhibits a red color in strongly acidic solutions, turning yellow in neutral to alkaline conditions.

The specific pH range over which a pHmérkkel changes color is known as its transition range. This range is determined by the acid dissociation constant (pKa) of the indicator. By using different pHmérkkel with overlapping transition ranges, chemists can determine the approximate pH of a solution with reasonable accuracy. This makes them valuable tools in titrations and general laboratory work for quick pH estimations.