Abstract:

Discussion on the influences of the indicators in acid-base titration had been made based on theoretical calculations and experiments. The pH changes using general expression of acid-base titration were calculated when bromothymol blue and phenolphthalein were used as the indictors in the titration of HCl with NaOH. The results showed that too high or low concentration of the indicators did not help identify the end point. A proper concentration of indicator is the guarantee of sensitive color change, and thus the accuracy of the titration.

Key words: Acid-base titration, Concentration of indicator, Bromothymol blue, Phenolphthalein