Acids, Bases, and Salts
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Free Chemistry Q & A Practice 1 of 5 free exam-style exercises in this topic
\(25.0\ \text{cm}^3\) of \(0.100\ \text{mol dm}^{-3}\) ethanoic acid was titrated with \(0.100\ \text{mol dm}^{-3}\) sodium hydroxide, and the pH was monitored. The titration curve and the properties of four indicators are shown.

0 5 10 15 20 25 30 35 40 45 50 0 2 4 6 8 10 12 14 equivalence point (25.0 cm3, pH 8.7) Volume of 0.100 mol dm−3 NaOH(aq) added / cm3 pH


Indicator pH range of colour change Colour (acid → alkali)
Methyl orange 3.1 – 4.4 red → yellow
Methyl red 4.2 – 6.3 red → yellow
Bromothymol blue 6.0 – 7.6 yellow → blue
Phenolphthalein 8.3 – 10.0 colourless → pink


Which indicator is the most suitable for this titration, and why?
Select one option.
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