AP Chemistry Unit 7.10: Q and K Response

Practice AP Chemistry Unit 7.10 questions on comparing Q with K after a disturbance and predicting how concentrations redistribute to reach equilibrium.

Exam points

Use stoichiometric and molecular models to analyze reactions, composition, and quantities from chemical evidence.
Calculate mass, moles, concentration, and formula relationships using balanced equations and measured data.

Covered syllabus points

7.10.A—Explain the relationships between Q, K, and the direction in which a reversible reaction will proceed to reach…

[Maximum number: 1]

Answer the following questions about magnesium.

The dissolution of magnesium hydroxide is represented by the following equation.

\mathrm{Mg}(\mathrm{OH})_{2}(s) \rightleftarrows \mathrm{Mg}^{2+}(a q)+2 \mathrm{OH}^{-}(a q) \quad K_{s p}=5.61 \times 10^{-12}

Using the reaction quotient, Q, predict whether a precipitate should form as the mixture

in beaker 3 approaches equilibrium. Justify your answer.

(iii) For the correct prediction and justification, consistent with part E (ii).

Examples of acceptable responses may include the following:

- $Q>K_{s p}$ , so a precipitate will form.

- The concentration of the ions in solution (represented by Q) is greater than that of a saturated solution, so a precipitate will form.

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Covered syllabus points

7.10 Reaction Quotient and Le Châtelier’s Principle question 1