Here's why:
* Aniline is a weak base: It can accept a proton (H+) to form its conjugate acid, but it's not a strong enough base to cause phenolphthalein to change color.
* Phenolphthalein is an acid-base indicator: It changes color based on the pH of the solution. In acidic solutions, it's colorless. In basic solutions, it turns pink.
* No reaction occurs: Aniline doesn't have a significant impact on the pH of the solution, so phenolphthalein will remain colorless in its presence.
To see a color change with phenolphthalein, you need to add a strong base like sodium hydroxide (NaOH). The reaction would look like this:
NaOH (aq) + HIn (aq) ⇌ NaIn (aq) + H2O (l)
* HIn represents the colorless form of phenolphthalein.
* NaIn represents the pink form of phenolphthalein.
In summary:
* Aniline and phenolphthalein don't react.
* Phenolphthalein's color change is due to its interaction with strong bases, not weak bases like aniline.
