Question

why is bromophenol blue and not phenolphthalein used as an indicator for the antacid titration

Answer 1

A acid base indicator gives a physical indication of acidity or basisity of the solution.The indicator is usually a organic dye and its colour change depends upon the pH. Antacids are bases and can titrated by acids for their estimation.hence acid base indicator must be used to detect the endpoint.

phenolphthalein is acid base indicatoe which can chage colour at pH= 8.3 to 10.

the pH range another acid base indicator bromophenol blue indicator is : pH:= 3.0 (BLUE)to 4.6 (YELLOW)

if u have pink tablet as antacid, the colur change cannot be perfectly identified because basic solution(antacid) is pink and phenolpthalein is blue in base., hence it is better to use bromophenol blue