- [Voiceover] The pH at
the equivalence point of the titration is measured to be 2.54. Which of the following indicators would be the best choice for determining the end point of the titration? Justify your answer. Well let's just remind ourselves, the endpoint of the titration is when the indicator changes color, and because that's our
signal, our visual signal, it's saying, "Hey, we must've
hit the equivalence point," you want the pKa of your indicator to be as close as possible to the pH at the equivalence point. If the pH at the
equivalence point is 2.54, well which of these indicators
have the closes pKa to that? Well we see thymol blue has
it at two right over here, so we would choose to use thymol blue, thymol blue, because its pKa closest to pH at equivalence point. Equivalence, equivalence point. There you go.