When you mix water and phenolphthalein, the solution remains colorless. Phenolphthalein is an indicator that changes color in the presence of a base (alkaline solution). In pure water, which is neutral, phenolphthalein remains colorless.
Understanding Phenolphthalein
Phenolphthalein is a chemical compound that is commonly used as an indicator in acid-base titrations. It is a weak acid that exists in two forms:
- Colorless form: In acidic solutions, phenolphthalein exists in its colorless form.
- Pink form: In basic solutions, phenolphthalein changes to its pink form.
The Role of pH
The color change of phenolphthalein is dependent on the pH of the solution. Here's a breakdown:
- pH < 8.2: Colorless
- pH > 10.0: Pink
Pure water has a pH of 7, which falls within the range where phenolphthalein remains colorless.
Practical Example
Imagine adding a few drops of phenolphthalein solution to a beaker of pure water. The solution will remain colorless. However, if you add a strong base like sodium hydroxide (NaOH) to the solution, the pH will increase, and the solution will turn pink.
In Summary
Mixing water and phenolphthalein results in a colorless solution. This is because phenolphthalein only changes color in the presence of a base. Pure water is neutral, so the indicator remains colorless.
