At a pH greater than 8.3, phenolphthalein is what color?

Phenolphthalein is a pH indicator commonly used in titrations and various laboratory analyses. Its color changes depending on the acidity or alkalinity of a solution. At a pH less than approximately 8.3, phenolphthalein is colorless, indicating that the solution is acidic to neutral. However, as the pH rises above this threshold, it undergoes a structural change that results in the formation of a colored compound.

When the pH exceeds 8.3, phenolphthalein turns pink, indicating a basic or alkaline condition. This is due to deprotonation of the phenolphthalein molecule, which leads to the intensification of its color. The transition between these states provides a clear visual representation for chemists to determine the pH of the solution being tested.

The other color choices do not align with the behavior of phenolphthalein at higher pH levels. Clear would represent an acidic solution, while blue and green are not recognized colors for phenolphthalein in any pH range typically encountered in laboratory environments. Thus, pink is the distinct color that signifies a basic solution when measured with phenolphthalein as the indicator.