Question

A synthetic indicator phenolphthalein gives ________ colour in basic solution.

• A. Red
• B. Blue
• C. Pink
• D. Colorless

Answer 1

The correct option is C Pink

Phenolphthalein is often used as an indicator in acid-base titrations. It turns colourless in acidic solutions and pink in basic solutions. Phenolphthalein is slightly soluble in water and usually dissolved in alcohols for use in experiments. It is a weak acid that can lose $H^{+}$ ions in solution. Phenolphthalein molecule is colourless and phenolphthalein ion is pink in colour. When a base is added to phenolphthalein, the molecule turns into ions leading to more ionization as $H^{+}$ ions are removed.