Phenolphthalein is a chemical compound that is often used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range at which phenolphthalein changes color is from 8.2 to 10.6.

Sodium carbonate is a basic compound, but its pH is not high enough to cause phenolphthalein to change color. The pH of a 0.1 M solution of sodium carbonate is about 11.5, which is above the pH range at which phenolphthalein changes color. Therefore, sodium carbonate does not react with phenolphthalein indicator.