Posted by Lucy on .
Phenolphthalein is an indicator that changes colour to pink/purple between pH 8-->10, however, neutralization occurs when pH=7. Why can phenolphthalein still be used as the indicator during a strong acid-strong base titration with virtually no error?
Because ih the titration of a strong acid with a strong base the titration curve is so steep near the equivalence point that one drop of the titrant will change the pH from about 3 or 4 to about 10 or 11; therefore, virtually no titration error occurs.
A student performing this experiment forgot to add phenolphthalein solution to the vinegar solution
before beginning the titration. After adding 27 mL of NaOH solution, he realized his error and added the
indicator. The solution turned bright pink. Suggest a procedure the student could follow to salvage the titration.