For a strong-acid, strong-base titration with a ph equivalence point at 7, why can we use bromophenol blue indicator? (NaOH, HCl reaction)

Answer 1

In addition to what Jacques D. answered, I'd add that almost all students will be able to easily see the color change at the equivalence point. As a red-weak-color-blind chemist who occasionally in my career had to strain to detect things like oil rancidity test endpoints, or Fajans titration endpoints, I appreciate such a nice indicator like that!

-- Cheers, --Mr. d.

Answer 2

You should use the indicator that has a pKA = pH at the equivalence point. For a strong acid and base, the pH is that of water (7) which is when BTB changes color. You can actually use just about any indicator because the pH is changing very rapidly and could go to a pH of 4 to 9 in a fraction of a drop from the buret. Nontheless, BTB is best for this situation.

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