Answer to Question #92970 in General Chemistry for cholo polco

Question

The color change at the endpoint should persist for 30 seconds. Explain why the time lapse is a good titration technique. Answer in 4 sentences.

Answer 1

After you add the single drop of the titrant, you always have to wait when the reaction is complete. When the titration is just started, the concentration of the titrated substance is still high enough for the relatively fast reaction and you will see the end of it just immediately. However, the closer the end point, the lower is the concentration of the titrated substance and it will react slower and slower. Thus, there are two main reasons to wait approximately 30 sec.: let the reagents to be uniformly mixed together and let the reaction to be complete even at low concentration of the titrated substance near the end point (this will prevent the underestimation of the real end point).