AP Chemistry Unit 4.8: Brønsted-Lowry Acids and Bases

Practice AP Chemistry Unit 4.8 questions on identifying Brønsted-Lowry acids, bases, and conjugate pairs, then writing aqueous proton-transfer equations.

Exam points

Use acid–base and solubility equilibria to predict pH, precipitation, and species changes in aqueous reactions.
Calculate equilibrium concentrations, K values, and titration quantities from balanced equations and measured data.

Covered syllabus points

4.8.A—Identify species as BrønstedLowry acids, bases, and/or conjugate acid-base pairs, based on proton-transfer…

[Maximum number: 1]

Answer the following questions about the glycolate ion, $\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{3}{ }^{-}$ , which acts as a base in

aqueous solution. A Lewis diagram for the ion is provided.

Figure for Question 4.8 Introduction to Acid-Base Reactions question 1 — AP Chemistry

On the Lewis diagram in part A, circle the atom that accepts the proton when the glycolate

ion reacts with water.

When the glycolate ion reacts with water, it forms glycolic acid, $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{3}$ , according to the

following equation. The $K_{b}$ expression for the reaction is provided.

\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{3}^{-}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftarrows \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{3}(a q)+\mathrm{OH}^{-}(a q) \quad K_{b}=\frac{\left[\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{3}\right]\left[\mathrm{OH}^{-}\right]}{\left[\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{3}^{-}\right]}

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Covered syllabus points

4.8 Introduction to Acid-Base Reactions question 1