---
title: "A student investigates the effect of \\(\\text{pH}\\) on the solubility of three hypothetical sparingly soluble salts: \\(\\text{MX}\\), \\(\\text{MY}\\), and \\(\\text{MZ}\\). Each salt has a \\(1:1\\) cation-to-anion ratio and dissolves according to the generic equation:  \\[ \\text{MA(s)} \\rightleftharpoons \\text{M}^+\\text{(aq)} + \\text{A}^-\\text{(aq)} \\]  The student gathers the equilibrium data shown in the table below at \\(298\\text{ K}\\).  | Salt | \\(K_{sp}\\) at \\(298\\text{ K}\\) | Anion | \\(pK_b\\) of Anion at \\(298\\text{ K}\\) | | :— | :— | :— | :— | | \\(\\text{MX}\\) | \\(1.0 \\times 10^{-10}\\) | \\(\\text{X}^-\\) | \\(4.2\\) | | \\(\\text{MY}\\) | \\(1.0 \\times 10^{-8}\\) | \\(\\text{Y}^-\\) | \\(9.5\\) | | \\(\\text{MZ}\\) | \\(1.0 \\times 10^{-6}\\) | \\(\\text{Z}^-\\) | \\(16.2\\) |  Equal volumes of saturated solutions of each salt (each in contact with excess solid) are treated with a strong acid to lower the \\(\\text{pH}\\) from \\(7.0\\) to \\(2.0\\). Which of the following correctly ranks the salts from greatest to least increase in molar solubility upon acidification, and provides the correct justification?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/123812/"
date_modified: "2026-09-28T12:30:23+00:00"
---

# A student investigates the effect of \(\text{pH}\) on the solubility of three hypothetical sparingly soluble salts: \(\text{MX}\), \(\text{MY}\), and \(\text{MZ}\). Each salt has a \(1:1\) cation-to-anion ratio and dissolves according to the generic equation:

\[ \text{MA(s)} \rightleftharpoons \text{M}^+\text{(aq)} + \text{A}^-\text{(aq)} \]

The student gathers the equilibrium data shown in the table below at \(298\text{ K}\).

| Salt | \(K_{sp}\) at \(298\text{ K}\) | Anion | \(pK_b\) of Anion at \(298\text{ K}\) |
| :— | :— | :— | :— |
| \(\text{MX}\) | \(1.0 \times 10^{-10}\) | \(\text{X}^-\) | \(4.2\) |
| \(\text{MY}\) | \(1.0 \times 10^{-8}\) | \(\text{Y}^-\) | \(9.5\) |
| \(\text{MZ}\) | \(1.0 \times 10^{-6}\) | \(\text{Z}^-\) | \(16.2\) |

Equal volumes of saturated solutions of each salt (each in contact with excess solid) are treated with a strong acid to lower the \(\text{pH}\) from \(7.0\) to \(2.0\). Which of the following correctly ranks the salts from greatest to least increase in molar solubility upon acidification, and provides the correct justification?

A student investigates the effect of \(\text{pH}\) on the solubility of three hypothetical sparingly soluble salts: \(\text{MX}\), \(\text{MY}\), and \(\text{MZ}\). Each salt has a \(1:1\) cation-to-anion ratio and dissolves according to the generic equation:

\[ \text{MA(s)} \rightleftharpoons \text{M}^+\text{(aq)} + \text{A}^-\text{(aq)} \]

The student gathers the equilibrium data shown in the table below at \(298\text{ K}\).

| Salt | \(K_{sp}\) at \(298\text{ K}\) | Anion | \(pK_b\) of Anion at \(298\text{ K}\) |
| :--- | :--- | :--- | :--- |
| \(\text{MX}\) | \(1.0 \times 10^{-10}\) | \(\text{X}^-\) | \(4.2\) |
| \(\text{MY}\) | \(1.0 \times 10^{-8}\) | \(\text{Y}^-\) | \(9.5\) |
| \(\text{MZ}\) | \(1.0 \times 10^{-6}\) | \(\text{Z}^-\) | \(16.2\) |

Equal volumes of saturated solutions of each salt (each in contact with excess solid) are treated with a strong acid to lower the \(\text{pH}\) from \(7.0\) to \(2.0\). Which of the following correctly ranks the salts from greatest to least increase in molar solubility upon acidification, and provides the correct justification?

- **A.** \(\text{MZ} > \text{MY} > \text{MX}\), because \(\text{MZ}\) has the largest \(K_{sp}\) value, resulting in the highest initial concentration of dissolved anions available to react with \(\text{H}^+\text{(aq)}\).
- **B.** \(\text{MZ} > \text{MY} > \text{MX}\), because a larger \(pK_b\) corresponds to a stronger base, causing \(\text{Z}^-\text{(aq)}\) to accept protons more readily and shift the dissolution equilibrium further to the right.
- **C.** \(\text{MX} > \text{MY} > \text{MZ}\), because salts with smaller \(K_{sp}\) values have lower lattice energies, making their solid lattices more susceptible to chemical breakdown by acid.
- **D.** \(\text{MX} > \text{MY} > \text{MZ}\), because \(\text{X}^-\text{(aq)}\) has the smallest \(pK_b\) and is therefore the strongest base, which reacts most extensively with \(\text{H}^+\text{(aq)}\) to remove dissolved anions and shift the dissolution equilibrium to the right.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123812/*