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title: "A student prepares a buffer solution by dissolving equimolar amounts of a weak acid, \\(\\text{HA}\\), and its conjugate base, \\(\\text{NaA}\\), in distilled water at \\(25^\\circ\\text{C}\\). The ionization of \\(\\text{HA(aq)}\\) is represented by the equation below.  \\[\\text{HA(aq)} + \\text{H}_2\\text{O(l)} \\rightleftharpoons \\text{A}^-\\text{(aq)} + \\text{H}_3\\text{O}^+\\text{(aq)} \\quad \\Delta H^\\circ > 0\\]  The solution is subsequently heated from \\(25^\\circ\\text{C}\\) to \\(50^\\circ\\text{C}\\). Assuming the volume of the solution remains constant, which of the following correctly predicts the effect of this temperature increase on the acid-dissociation constant, \\(K_a\\), and the \\(\\text{pH}\\) of the buffer solution?"
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url: "https://nerd-notes.com/ubq/123775/"
date_modified: "2026-09-28T12:30:15+00:00"
---

# A student prepares a buffer solution by dissolving equimolar amounts of a weak acid, \(\text{HA}\), and its conjugate base, \(\text{NaA}\), in distilled water at \(25^\circ\text{C}\). The ionization of \(\text{HA(aq)}\) is represented by the equation below.

\[\text{HA(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{A}^-\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \Delta H^\circ > 0\]

The solution is subsequently heated from \(25^\circ\text{C}\) to \(50^\circ\text{C}\). Assuming the volume of the solution remains constant, which of the following correctly predicts the effect of this temperature increase on the acid-dissociation constant, \(K_a\), and the \(\text{pH}\) of the buffer solution?

A student prepares a buffer solution by dissolving equimolar amounts of a weak acid, \(\text{HA}\), and its conjugate base, \(\text{NaA}\), in distilled water at \(25^\circ\text{C}\). The ionization of \(\text{HA(aq)}\) is represented by the equation below.

\[\text{HA(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{A}^-\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \Delta H^\circ > 0\]

The solution is subsequently heated from \(25^\circ\text{C}\) to \(50^\circ\text{C}\). Assuming the volume of the solution remains constant, which of the following correctly predicts the effect of this temperature increase on the acid-dissociation constant, \(K_a\), and the \(\text{pH}\) of the buffer solution?

- **A.** \(K_a\) decreases and \(\text{pH}\) increases, because the forward reaction is endothermic and higher temperatures shift the equilibrium toward the reactants.
- **B.** \(K_a\) remains unchanged and \(\text{pH}\) remains unchanged, because buffer solutions resist changes in \(\text{pH}\) when external conditions change.
- **C.** \(K_a\) increases and \(\text{pH}\) decreases, because the forward reaction is endothermic and higher temperatures shift the equilibrium toward the products, increasing \([\text{H}_3\text{O}^+]\).
- **D.** \(K_a\) increases and \(\text{pH}\) increases, because shifting the equilibrium toward the products increases \([\text{A}^-]\), making the solution more basic.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123775/*