---
title: "A student investigates the dissolution of a sparingly soluble ionic compound, \\(\\text{MX}_2(s)\\), in pure water according to the following process:  \\[ \\text{MX}_2(s) \\rightleftharpoons \\text{M}^{2+}(aq) + 2\\,\\text{X}^-(aq) \\quad \\Delta H^\\circ_{\\text{soln}} > 0 \\]  At \\(298\\text{ K}\\), both \\(\\Delta G^\\circ_{\\text{soln}} > 0\\) and \\(\\Delta S^\\circ_{\\text{soln}} > 0\\). The temperature of the saturated solution containing excess undissolved \\(\\text{MX}_2(s)\\) is increased from \\(298\\text{ K}\\) to \\(350\\text{ K}\\). Assuming \\(\\Delta H^\\circ_{\\text{soln}}\\) and \\(\\Delta S^\\circ_{\\text{soln}}\\) are independent of temperature over this range, which of the following correctly predicts the effect on the thermodynamic favorability of the dissolution process and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/123915/"
date_modified: "2026-09-28T12:32:09+00:00"
---

# A student investigates the dissolution of a sparingly soluble ionic compound, \(\text{MX}_2(s)\), in pure water according to the following process:

\[ \text{MX}_2(s) \rightleftharpoons \text{M}^{2+}(aq) + 2\,\text{X}^-(aq) \quad \Delta H^\circ_{\text{soln}} > 0 \]

At \(298\text{ K}\), both \(\Delta G^\circ_{\text{soln}} > 0\) and \(\Delta S^\circ_{\text{soln}} > 0\). The temperature of the saturated solution containing excess undissolved \(\text{MX}_2(s)\) is increased from \(298\text{ K}\) to \(350\text{ K}\). Assuming \(\Delta H^\circ_{\text{soln}}\) and \(\Delta S^\circ_{\text{soln}}\) are independent of temperature over this range, which of the following correctly predicts the effect on the thermodynamic favorability of the dissolution process and provides the correct justification?

A student investigates the dissolution of a sparingly soluble ionic compound, \(\text{MX}_2(s)\), in pure water according to the following process:

\[ \text{MX}_2(s) \rightleftharpoons \text{M}^{2+}(aq) + 2\,\text{X}^-(aq) \quad \Delta H^\circ_{\text{soln}} > 0 \]

At \(298\text{ K}\), both \(\Delta G^\circ_{\text{soln}} > 0\) and \(\Delta S^\circ_{\text{soln}} > 0\). The temperature of the saturated solution containing excess undissolved \(\text{MX}_2(s)\) is increased from \(298\text{ K}\) to \(350\text{ K}\). Assuming \(\Delta H^\circ_{\text{soln}}\) and \(\Delta S^\circ_{\text{soln}}\) are independent of temperature over this range, which of the following correctly predicts the effect on the thermodynamic favorability of the dissolution process and provides the correct justification?

- **A.** The dissolution becomes less thermodynamically favorable because increasing the temperature increases the thermal energy transferred to the surroundings, making \(\Delta S^\circ_{\text{surr}}\) more positive.
- **B.** The dissolution becomes more thermodynamically favorable because the \(-T\Delta S^\circ_{\text{soln}}\) term becomes more negative, causing \(\Delta G^\circ_{\text{soln}}\) to decrease.
- **C.** The dissolution becomes more thermodynamically favorable because \(\Delta H^\circ_{\text{soln}}\) decreases significantly at higher temperatures, lowering the activation energy barrier for ion separation.
- **D.** The dissolution becomes less thermodynamically favorable because solvent water molecules form more rigid hydration shells around the dissociated ions at higher temperatures, causing \(\Delta S^\circ_{\text{soln}}\) to become negative.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123915/*