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AP Chemistry Unit 8.1: pH and pOH

Practice AP Chemistry Unit 8.1 questions on pH measurement and the relationships among hydronium, hydroxide, pH, pOH, and neutral water.

Syllabus
Effective Fall 2025
Course
AP Chemistry

Exam points

  • Use stoichiometric and molecular models to analyze reaction quantities, composition, and limiting outcomes.
  • Calculate mass, moles, concentration, and formula relationships from balanced equations and measured data.

Covered syllabus points

8.1.A—Calculate the values of pH and pOH, based on Kw and the concentration of all species present in a neutral…

8.1 Introduction to Acids and Bases question 1

[Maximum number: 1]

A student is given 50.0 mL of a solution of Na2CO3\mathrm{Na}_{2} \mathrm{CO}_{3} of unknown concentration. To determine the concentration of the solution, the student mixes the solution with excess 1.0MCa(NO3)2(aq)1.0 M \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(a q), causing a precipitate to form. The balanced equation for the reaction is shown below.

Na2CO3(aq)+Ca(NO3)2(aq)→2NaNO3(aq)+CaCO3(s)\mathrm{Na}_{2} \mathrm{CO}_{3}(a q)+\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(a q) \rightarrow 2 \mathrm{NaNO}_{3}(a q)+\mathrm{CaCO}_{3}(s)

The student decides to first determine [ OH−\mathrm{OH}^{-}] in the solution, then use that result to calculate the initial concentration of CO32−(aq)\mathrm{CO}_{3}{ }^{2-}(a q).

Identify a laboratory method (not titration) that the student could use to collect data to determine [OH−]\left[\mathrm{OH}^{-}\right] in the solution.

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