Final answer:
Phenolphthalein indicator detects high pH. It is colorless below pH 9 and turns pink at pH 10 and above. It is suitable for titrations involving a weak acid.
Step-by-step explanation:
Phenolphthalein indicator detects high pH. It is colorless at pH values below 9 and turns pink at pH 10 and above. However, at very high pH, it becomes colorless again.
In a titration of a strong acid with a strong base, any indicator with a pKin between about 4.0 and 10.0 can be used. For a weak acid titration, indicators with pKin > 7.0, like phenolphthalein, are suitable. Conversely, for a weak base titration, indicators with pKin < 7.0, such as methyl red or bromocresol blue, should be used.
Acid-base indicators like phenolphthalein are weak organic compounds that change color within a specific pH range, depending on the presence of acid or base.