In titration, what is the purpose of the indicator?

• A. to measure the volume of alkali
• B. to determine when the reaction is complete
• C. to speed up the reaction
• D. to color the solution yellow

Answer: (B)

In titration, the indicator shows when the reaction has just finished by changing color at the point where the acid and base have neutralized each other. The color change happens at a pH that’s close to the equivalence point, so you can read the volume of titrant added from the burette to determine how much reactant was required. It doesn’t measure volume directly, nor does it speed up the reaction, and the indicator’s color isn’t fixed to yellow—it changes color according to the indicator chosen to signal the end of the reaction.