AP Chemistry Flashcards: pH and Solubility
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
If a salt contains a hydroxide ion (e.g., Mg(OH)₂), how will decreasing the pH (adding acid) affect its solubility?
Decreasing the pH will increase its solubility because the added H+ ions will react with and remove the OH- ions, shifting the equilibrium to favor more dissolution.
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If a salt contains a hydroxide ion (e.g., Mg(OH)₂), how will decreasing the pH (adding acid) affect its solubility?
Decreasing the pH will increase its solubility because the added H+ ions will react with and remove the OH- ions, shifting the equilibrium to favor more dissolution.
What is the fundamental reason that the solubility of some salts is dependent on pH?
The solubility is pH-dependent because at least one of the salt's ions can react with H+ or OH- in the solution, which disturbs the dissolution equilibrium.
Identify the three types of constituent ions that can make a salt's solubility pH-sensitive.
The three types of ions are weak acids, weak bases, and hydroxide ions.
Which scientific principle is used to qualitatively understand the effect of pH on solubility?
The effect of pH changes on the solubility of a salt can be qualitatively understood using Le Châtelier’s principle.
What is meant by the 'qualitative effect' of pH on solubility?
It refers to identifying whether a change in pH will cause the solubility of a salt to increase or decrease, without necessarily calculating the exact amount.
Would the solubility of NaCl be sensitive to changes in pH? Explain why or why not based on its constituent ions.
No, because its ions (Na+ and Cl-) are derived from a strong base and a strong acid, respectively, and are not weak acids or bases.
What characteristic must a salt possess for its solubility to be sensitive to pH?
The salt's solubility is pH-sensitive if one of its constituent ions is a weak acid, a weak base, or hydroxide.
How does Le Châtelier's principle connect pH and the solubility of a salt like calcium carbonate (CaCO₃), which contains a weak base (CO₃²⁻)?
Le Châtelier's principle explains that adding acid (H+) will react with the weak base ion (CO₃²⁻), causing the dissolution equilibrium to shift right and increase solubility.
Consider a salt containing the anion of a weak acid. How does applying Le Châtelier's principle explain why adding acid increases its solubility?
Adding acid (H+) removes the anion from the solution to form the weak acid, shifting the salt's dissolution equilibrium to the right to produce more ions.
pH-Sensitive Solubility
A property of a salt where its solubility is affected by changes in the pH of the solution.