Consider the following indicators and their pH ranges:
Methyl orange | 3.2-4.4 |
Methyl red | 4.8-6.0 |
Bromothymol blue | 6.0-7.6 |
Phenolphthalein | 8.2-10.0 |
Alizarin yellow | 10.1-12.0 |
Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range. For which of the following titrations would methyl red be the best indicator?
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0.100 M HNO3 + 0.100 M KOH◦
0.100 M aniline (Kb = 3.8 × 10–10) + 0.100 M HCl◦
0.100 M NH3 (Kb = 1.8 × 10–5) + 0.100 M HCl◦
0.100 M HF (Ka = 7.2 × 10–4) + 0.100 M NaOH◦
0.100 M acetic acid (Ka = 1.8 × 10–5) + 0.100 M NaOH