Phenolphthalein is a commonly used pH indicator that changes color based on the acidity or basicity of a solution. In acidic and neutral solutions, phenolphthalein turns colorless. This means that there is no visible color change observed when phenolphthalein is added to an acidic or neutral solution.
Here is a more detailed explanation:
Phenolphthalein as a pH indicator:
- Phenolphthalein is a weak acid that undergoes a color change depending on the concentration of hydrogen ions (H+) in a solution.
- In acidic solutions, there is a high concentration of H+ ions, which react with the phenolphthalein and cause it to become colorless.
- In basic solutions, there is a low concentration of H+ ions, allowing the phenolphthalein to remain in its colored form (pink or red, depending on the pH).
Color changes of phenolphthalein:
- Acidic solution (pH < 7):="" />
- Neutral solution (pH = 7): Colorless
- Basic solution (pH > 7): Pink or red
Significance of phenolphthalein's color change:
- The color change of phenolphthalein can be used to determine the acidity or basicity of a solution.
- In titration experiments, phenolphthalein is often used as an indicator to signal the endpoint of a reaction when the solution reaches a certain pH.
- Its colorless nature in acidic and neutral solutions makes it a suitable indicator for these pH ranges.
Conclusion:
Phenolphthalein is colorless in both acidic and neutral solutions. Its color change to pink or red occurs in basic solutions. By observing the color change of phenolphthalein, one can determine the pH of a solution.