SSC MTS EXAM

Detailed explanation-1: -An example of a weak acid indicator is phenolphthalein, which is colorless as a weak acid but dissociates in water to form a magenta or red-purple anion.

Detailed explanation-2: -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. It belongs to the class of dyes known as phthalein dyes.

Detailed explanation-3: -Phenolphthalein solution turns pink in the presence of a base. This is because the hydroxide ions react with the acidic group present and lead to the formation of ions. These ions impart color to the solution. This is how phenolphthalein solution acts as an acid-base indicator in titrations.