Question

Why did the colour of phenolphthalein change after the addition
of an acid?​

Answer 1

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The phenolphthalein indicator allows chemists to visually identify whether a substance is an acid or a base. The color change in phenolphthalein is a result of ionization, and this alters the shape of the phenolphthalein molecules.

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Answer 2

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Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.

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