AP Chemistry Unit 8.5: Acid-Base Titrations

Practice AP Chemistry Unit 8.5 questions on titration curves, pKa, analyte concentration, equivalence points, and indicator selection.

Exam points

Use electrochemical equations and reduction potentials to predict redox direction, cell voltage, and electrodes.
Relate electron transfer, stoichiometry, and charge balance to products and thermodynamic favorability.

[Maximum number: 1]

Answer the following questions about ascorbic acid (vitamin C).

Ascorbic acid, HAsc (a q), acts as a weak acid, as shown in the equation.

\mathrm{HAsc}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftarrows \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{Asc}^{-}(a q)

The following titration curve was produced when a 10.0 mL sample of HAsc (a q) was titrated

using $0.0550 M \mathrm{NaOH}(a q)$ .

From the titration curve, determine the approximate $\mathrm{p} K_{a}$ of ascorbic acid.

(ii) For the correct $\mathrm{p} K_{a}$ :

4.1 (acceptable range: 4.0-4.3)

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