Kleurindicatoren

Kleurindicatoren, also known as pH indicators, are chemical substances that change color at specific pH values. They are widely used in chemistry and biology to determine the acidity or alkalinity of a solution. These substances are typically weak acids or bases, and their color change is due to a reversible chemical reaction that alters their molecular structure. The two forms of the indicator, the acid form and the conjugate base form, absorb and reflect light differently, resulting in distinct colors.

The pH range over which an indicator changes color is called its transition range. Different indicators have different transition ranges, allowing for the measurement of a wide spectrum of pH values. For example, litmus paper, one of the most common indicators, turns red in acidic solutions (pH below 4.5) and blue in alkaline solutions (pH above 8.3). Phenolphthalein is another well-known indicator that is colorless in acidic solutions and pink in alkaline solutions, with a transition range between pH 8.2 and 10.0.

Kleurindicatoren are crucial in various applications. They are used in titrations to signal the endpoint, the point at which the reaction is complete. In environmental monitoring, they help assess water quality. They are also employed in educational settings to demonstrate acid-base concepts and in home use for tasks like testing swimming pool water or soil pH. The selection of an appropriate indicator depends on the expected pH range of the solution being tested.