AP Chemistry 8.11: pH and Salt Solubility

Practice AP Chemistry questions on predicting how pH changes the solubility of salts containing weak-acid, weak-base, or hydroxide ions.

Exam points

Explain how thermodynamic and kinetic factors influence chemical reaction behavior and outcomes.
Apply energy, equilibrium and rate concepts to predict reaction feasibility and speed.

[Maximum number: 1]

Answer the following questions about magnesium.

In a separate experiment, the student adds $\mathrm{HNO}_{3}(a q)$ to decrease the pH of a saturated

solution containing undissolved $\mathrm{Mg}(\mathrm{OH})_{2}(s)$ . Does the amount of undissolved $\mathrm{Mg}(\mathrm{OH})_{2}(s)$

increase, decrease, or remain the same as the $\mathrm{HNO}_{3}(a q)$ is added? Justify your answer.

F For the correct answer and justification:

Point 10

Decrease. The $\mathrm{H}^{+}$ from $\mathrm{HNO}_{3}(a q)$ will react with $\mathrm{OH}^{-}$ , decreasing [ $\mathrm{OH}^{-}$ ] and

causing $Q<K_{s p}$ . As a result, more $\operatorname{Mg}(\mathrm{OH})_{2}(s)$ will dissolve until equilibrium is

reestablished, resulting in less $\mathrm{Mg}(\mathrm{OH})_{2}(s)$ .

All question bank results loaded

8.11.A—Identify the qualitative effect of changes in pH on the solubility of a salt question 1