Phenolphthalein as a pH Indicator
Phenolphthalein is a widely used pH indicator that changes color based on the acidity or basicity of a solution.

Color Change in Acidic Solutions
- In acidic environments (pH < 7),="" phenolphthalein="" remains="" />
- This is due to the presence of hydrogen ions (H⁺) which keep the phenolphthalein molecule in its acidic form.

Color Change in Basic Solutions
- When the pH of the solution rises above 8.2, phenolphthalein begins to change color.
- In basic (alkaline) conditions (pH > 8.2), it transitions to a **pink** color.
- This pink color results from the deprotonation of the phenolphthalein molecule, forming its basic form which is colored.

Color Transition Range
- The transition from colorless to pink occurs between pH 8.2 to 10.0.
- At around pH 10, the solution is fully pink.

Applications of Phenolphthalein
- Phenolphthalein is commonly used in titrations to determine the endpoint of a reaction.
- It helps in differentiating between acidic and basic solutions effectively.
In summary, phenolphthalein is a useful pH indicator that changes from colorless in acidic solutions to pink in basic solutions, making it an important tool in chemistry for visualizing pH changes.