Phenolphthalein and NaOH Reaction with dilute HCl

Introduction:
When dilute HCl is added drop by drop to a solution of phenolphthalein and NaOH, a color change is observed.

Observation:
- Initially, the solution is pink in color due to the presence of phenolphthalein in a basic solution of NaOH.
- As dilute HCl is added drop by drop, the pink color gradually fades away.

Explanation:
- Phenolphthalein is a pH indicator that changes color in response to the pH of a solution.
- It is pink in basic solutions (pH > 8.2) and colorless in acidic solutions (pH < 8.2).="" -="" naoh="" is="" a="" strong="" base,="" which="" gives="" the="" initial="" pink="" color="" to="" the="" solution.="" -="" when="" dilute="" hcl="" is="" added,="" it="" neutralizes="" the="" base="" (naoh)="" present="" in="" the="" solution.="" -="" as="" the="" ph="" decreases="" due="" to="" the="" addition="" of="" hcl,="" phenolphthalein="" loses="" its="" pink="" color="" and="" becomes="" colorless.="" />

Conclusion:
- The color change from pink to colorless indicates the neutralization of the base by the acid.
- This experiment demonstrates the concept of pH indicators and the reaction between acids and bases.