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AP Chemistry 8.1: pH and pOH

Practice AP Chemistry questions on identifying pH measurement methods and relating hydronium, hydroxide, pH, pOH, and neutral water.

Syllabus
Effective Fall 2025
Course
AP Chemistry

Exam points

  • Explain how intermolecular forces and particle motion determine physical properties of substances.
  • Apply molecular models to predict phase behavior, boiling point and solubility from particle interactions.

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