What color does phenolphthalein indicate in an acidic solution?

• A. Purple
• B. Yellow
• C. Clear
• D. Blue

Answer: (C)

Phenolphthalein is a pH indicator that changes color based on how acidic or basic the solution is. In acidic solutions, the form of the molecule present has no color, so the solution appears colorless (clear). Only when the solution becomes basic does phenolphthalein turn pink. So in an acidic solution, the color you’d observe is clear.