Using Figure 17.11, suggest an indicator to use in each of...

Using Figure 17.11, suggest an indicator to use in each of the following titrations.
(a) $\mathrm{NaHCO}_3$ is titrated to $\mathrm{CO}_3{ }^{2-}$ with $\mathrm{NaOH}$.
(b) Hypochlorous acid is titrated with $\mathrm{NaOH}$.
(c) Trimethylamine is titrated with $\mathrm{HCl}$.

Key Concepts

Acid-Base Titrations

Acid-base titrations involve gradually adding an acid or base to a solution until the point of complete neutralization is achieved. Monitoring the change in pH as the titrant is added allows for the determination of key aspects of the reaction, such as the equivalence point, which is essential for accurate quantitative analysis.

Equivalence Point

The equivalence point is reached when stoichiometrically equivalent amounts of the titrant and analyte have reacted. Its pH depends on the strength of the acids and bases involved. Identifying the equivalence point accurately is crucial for the correct interpretation of titration data and for selecting a suitable indicator.

pH Indicators

pH indicators are chemical compounds that change color over a specific range of pH values. They signal the endpoint of a titration by exhibiting a noticeable color change. Choosing the right pH indicator is essential to match the pH at the equivalence point, ensuring precise detection of the titration's endpoint.

Indicator Transition Range

The indicator transition range is the narrow pH interval over which an indicator undergoes a color change. It is important that this range aligns with the pH shift at the equivalence point of the titration so that a clear and accurate signal is provided at the moment of neutralization.

Reaction Characteristics in Titrations

Different acid-base titrations, such as those involving weak acids or bases with their strong counterparts, yield titration curves with distinct shapes and equivalence point pH values. Understanding these reaction characteristics is important for selecting an appropriate indicator as it dictates the optimal pH region for the color change.

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