pHindikátorok

pHindikátorok, often referred to as acid-base indicators, are chemical substances that exhibit a visible color change at a specific pH value or range. This change occurs because the indicator molecule undergoes a reversible chemical reaction, typically involving the gain or loss of a proton (H+), which alters its electronic structure and therefore its absorption of light. Different indicator molecules have different pKa values, meaning they will change color at different pH levels.

The most common type of pH indicator is a dye. When dissolved in a solution, the indicator exists in equilibrium between its acidic and basic forms. In an acidic solution, the equilibrium shifts towards one form, resulting in a particular color. As the pH increases and the solution becomes more alkaline, the equilibrium shifts to the other form, producing a different color. Litmus paper, a well-known example, turns red in acidic solutions and blue in alkaline solutions. Other indicators like phenolphthalein change from colorless in acidic conditions to pink in alkaline conditions, while methyl orange turns red in acid and yellow in base.

pH indicators are widely used in various fields, including chemistry laboratories for titrations, environmental monitoring to test water acidity, and even in everyday life for simple pH tests. The choice of indicator depends on the expected pH range of the solution being tested. For precise pH measurements, digital pH meters are preferred, but indicators offer a quick, visual, and cost-effective alternative for many applications.