---
title: "A student prepares a saturated aqueous solution of magnesium hydroxide in equilibrium with undissolved solid at \\(25^\\circ\\text{C}\\), as represented by the equation below.  \\[\\text{Mg(OH)}_2(s) \\rightleftharpoons \\text{Mg}^{2+}(aq) + 2\\,\\text{OH}^-(aq)\\]  If several drops of \\(6.0\\text{ M }\\text{HCl}(aq)\\) are added to the mixture with constant stirring while the temperature remains at \\(25^\\circ\\text{C}\\), which of the following best predicts the effect on the solubility of \\(\\text{Mg(OH)}_2(s)\\) and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/120274/"
date_modified: "2026-08-23T04:04:12+00:00"
---

# A student prepares a saturated aqueous solution of magnesium hydroxide in equilibrium with undissolved solid at \(25^\circ\text{C}\), as represented by the equation below.

\[\text{Mg(OH)}_2(s) \rightleftharpoons \text{Mg}^{2+}(aq) + 2\,\text{OH}^-(aq)\]

If several drops of \(6.0\text{ M }\text{HCl}(aq)\) are added to the mixture with constant stirring while the temperature remains at \(25^\circ\text{C}\), which of the following best predicts the effect on the solubility of \(\text{Mg(OH)}_2(s)\) and provides the correct justification?

A student prepares a saturated aqueous solution of magnesium hydroxide in equilibrium with undissolved solid at \(25^\circ\text{C}\), as represented by the equation below.

\[\text{Mg(OH)}_2(s) \rightleftharpoons \text{Mg}^{2+}(aq) + 2\,\text{OH}^-(aq)\]

If several drops of \(6.0\text{ M }\text{HCl}(aq)\) are added to the mixture with constant stirring while the temperature remains at \(25^\circ\text{C}\), which of the following best predicts the effect on the solubility of \(\text{Mg(OH)}_2(s)\) and provides the correct justification?

- **A.** The solubility decreases because \(\text{H}^+(aq)\) ions react with \(\text{Mg}^{2+}(aq)\) ions, shifting the equilibrium to the left to favor the solid reactant.
- **B.** The solubility decreases because adding \(\text{HCl}(aq)\) increases the total dissolved ion concentration, causing \(Q\) to exceed \(K_{sp}\).
- **C.** The solubility increases because the neutralization reaction between \(\text{H}^+(aq)\) and \(\text{OH}^-(aq)\) releases heat, which increases the value of \(K_{sp}\).
- **D.** The solubility increases because \(\text{H}^+(aq)\) ions react with \(\text{OH}^-(aq)\) ions to form \(\text{H}_2\text{O}(l)\), lowering \([\text{OH}^-]\) so that \(Q < K_{sp}\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120274/*