Thymol blue in its acid range is not a suitable indicator for the titration of HCl by NaOH. Suppose that a student uses thymol blue by mistake in the titration of Figure 17-8 and that the indicator end point is taken to be pH = 2.0.

(a) Would there be a sharp color change, produced by the addition of a single drop of NaOH(aq)?

(b) Approximately what percent of the HCl remains unneutralized at pH = 2.0?

Figure 17-8

Transcribed Image Text:

Hd 14.0- 12.0 10.0 8.0 6.0 4.0 T | 2.0- 0.0- 5.0 Equivalence point- 10.0 pH range, alizarin yellow-R pH range, phenolphthalein pH range, bromthymol blue pH range, methyl red pH range, bromphenol blue pH range, thymol blue 25.0 30.0 35.0 40.0 45.0 15.0 20.0 Volume of 0.100 M NaOH, mL 50.0