CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Aniline (C6H5NH2) is a weak base with Kb=4.3×10−10. A 50.0mL sample of 0.120M aniline is titrated with 0.100M HCl to its equivalence point at 25 °C. Which indicator is most appropriate for this titration end-point?
Indicator acid–base transition ranges:
• Phenolphthalein: pH 8.2–10.0
• Bromcresol green: pH 3.8–5.4
• Methyl orange: pH 3.1–4.4
• Thymol blue (second range): pH 8.0–9.6
(a) Phenolphthalein
(b) Methyl orange
(c) Bromcresol green
(d) Thymol blue