Phenoliftaleiinipäätepiste

Phenoliftaleiinipäätepiste refers to the point in a titration where the indicator phenolphthalein changes color, signaling the completion of a chemical reaction. Phenolphthalein is a common acid-base indicator that is colorless in acidic solutions and pink or magenta in basic solutions. The color change occurs within a specific pH range, typically between pH 8.2 and 10.0.

In a titration, one solution of known concentration is gradually added to another solution of unknown concentration. The phenoliftaleiinipäätepiste is reached when the amount of titrant added is just enough to neutralize the analyte. If a titration involves a strong acid and a weak base, phenolphthalein can be used to detect the endpoint. As the base is added to the acid, the solution remains colorless until all the acid is neutralized and a slight excess of base is present. At this point, the pH rises into the range where phenolphthalein turns pink.

Conversely, in the titration of a strong base with a strong acid, phenolphthalein is generally not the preferred indicator because the equivalence point occurs at a pH of 7, which is outside the color change range of phenolphthalein. However, if the titration involves a weak acid and a strong base, phenolphthalein is an excellent choice. The endpoint, indicated by the persistent faint pink color, signifies that all the weak acid has been neutralized by the strong base. The specific color observed at the endpoint can vary slightly depending on the concentration of the solutions and the sensitivity of the observer.