Phenolphthalein in alkaline solution is which color?

Phenolphthalein in alkaline solution is which color?

• A. Colourless
• B. Pink
• C. Red
• D. Blue

Answer: (B)

Phenolphthalein acts as an acid–base indicator that changes color with pH. In acidic solutions it is colorless, but in alkaline solutions it becomes pink, with the shade deepening as the solution is more basic. The transition occurs around pH 8.2–10, so in alkaline conditions you observe pink. It doesn’t turn red or blue—those colors belong to other indicators.

Phenolphthalein acts as an acid–base indicator that changes color with pH. In acidic solutions it is colorless, but in alkaline solutions it becomes pink, with the shade deepening as the solution is more basic. The transition occurs around pH 8.2–10, so in alkaline conditions you observe pink. It doesn’t turn red or blue—those colors belong to other indicators.