Question

What will you observe when a drop of phenolphthalein is added?

Answer 1

Addition of phenolphthalein to the solution of lime water

• Lime water or calcium hydroxide $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ is basic in nature.
• Phenolphthalein $\left({\mathrm{C}}_{20}{\mathrm{H}}_{14}{\mathrm{O}}_4\right)$ is an acid-base indicator.
• It turns colorless in an acidic medium and pinkish in a basic medium.
• So, adding phenolphthalein to a solution of lime water turns the solution pinkish.
• Therefore, the addition of phenolphthalein turns the lime-water solution pinkish.