When does phenolphalien turn pink

Answer : Phenolphalien turn pink in the presence of a base.

Phenolphthalien : It is an indicator which is used in the acid-base titration.

In acidic medium, the phenolphthalien is colorless and the pH will be less than 7.

In basic medium, the phenolphthalien is pink in color and the pH will be greater than 7.

Phenolphthalien is slightly soluble in the water and highly soluble in alcohols.

Hence, the phenolphalien turn pink in the presence of a base.