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Chemistry · Unit 3 · Chemical equilibrium systems · Chemical equilibrium

Analyse data to determine an appropriate indicator given the equivalence point of the titration and the pH range of the indicator (assuming indicators change colour over a range of pKa ± 1). Volumetric analysis

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Question 1

A titration is performed between \(25.0\) mL of \(0.150\) mol L\(^{-1}\) ethanoic acid (\(\text{CH}_3\text{COOH}\), \(K_a = 1.8 \times 10^{-5}\)) and \(0.150\) mol L\(^{-1}\) sodium hydroxide (NaOH). The equivalence point occurs when \(25.0\) mL of NaOH has been added, and the pH at the equivalence point is \(8.87\). Three indicators are available, with their \(\text{p}K_a\) values listed in the table below. Analyse the data to determine which indicator is most suitable for this titration and justify your choice using the pH range over which the indicator changes colour.

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