Final answer:
Phenolphthalein is a pH indicator used to detect high pH levels (basic solutions), where it transitions from colorless to pink at around pH 9.2, indicating a slightly alkaline solution. It does not detect low pH (acidic) conditions.
Step-by-step explanation:
Phenolphthalein is a pH indicator that is commonly used to detect the presence of base in a solution. This compound is colorless in acidic to neutral solutions (below pH 8.3) and turns pink to deep pink in basic solutions (above pH 8.3), but it can turn colorless again at very high pH levels.
In the laboratory, phenolphthalein is added to a solution and then a base is slowly added. The change from colorless to pink indicates that the solution has reached a pH value where phenolphthalein changes color, around 9.2, which means it has become slightly alkaline. Phenolphthalein is therefore not suitable for detecting low pH values, as it is designed to detect high pH levels indicative of a basic solution.