---
title: "A student prepares a buffer at \\(25^\\circ\\text{C}\\) by mixing the solutions shown in the table. The \\(pK_a\\) of \\(\\text{HA(aq)}\\) is \\(5.00\\).  | Solution | Concentration | Volume | |———-|—————|——–| | \\(\\text{HA(aq)}\\) | \\(0.300\\text{ M}\\) | \\(50.0\\text{ mL}\\) | | \\(\\text{NaOH(aq)}\\) | \\(0.100\\text{ M}\\) | \\(50.0\\text{ mL}\\) |  The \\(\\text{OH}^-\\text{(aq)}\\) reacts completely with \\(\\text{HA(aq)}\\) according to \\(\\text{HA(aq)}+\\text{OH}^-\\text{(aq)}\\rightarrow\\text{A}^-\\text{(aq)}+\\text{H}_2\\text{O(l)}\\). Which of the following correctly predicts the pH of the resulting buffer relative to the \\(pK_a\\) of \\(\\text{HA(aq)}\\)?"
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date_modified: "2026-08-19T12:40:16+00:00"
---

# A student prepares a buffer at \(25^\circ\text{C}\) by mixing the solutions shown in the table. The \(pK_a\) of \(\text{HA(aq)}\) is \(5.00\).

| Solution | Concentration | Volume |
|———-|—————|——–|
| \(\text{HA(aq)}\) | \(0.300\text{ M}\) | \(50.0\text{ mL}\) |
| \(\text{NaOH(aq)}\) | \(0.100\text{ M}\) | \(50.0\text{ mL}\) |

The \(\text{OH}^-\text{(aq)}\) reacts completely with \(\text{HA(aq)}\) according to \(\text{HA(aq)}+\text{OH}^-\text{(aq)}\rightarrow\text{A}^-\text{(aq)}+\text{H}_2\text{O(l)}\). Which of the following correctly predicts the pH of the resulting buffer relative to the \(pK_a\) of \(\text{HA(aq)}\)?

A student prepares a buffer at \(25^\circ\text{C}\) by mixing the solutions shown in the table. The \(pK_a\) of \(\text{HA(aq)}\) is \(5.00\).

| Solution | Concentration | Volume |
|----------|---------------|--------|
| \(\text{HA(aq)}\) | \(0.300\text{ M}\) | \(50.0\text{ mL}\) |
| \(\text{NaOH(aq)}\) | \(0.100\text{ M}\) | \(50.0\text{ mL}\) |

The \(\text{OH}^-\text{(aq)}\) reacts completely with \(\text{HA(aq)}\) according to \(\text{HA(aq)}+\text{OH}^-\text{(aq)}\rightarrow\text{A}^-\text{(aq)}+\text{H}_2\text{O(l)}\). Which of the following correctly predicts the pH of the resulting buffer relative to the \(pK_a\) of \(\text{HA(aq)}\)?

- **A.** The pH is greater than \(pK_a\), because producing some \(\text{A}^-\text{(aq)}\) makes the conjugate base the predominant buffer component.
- **B.** The pH is equal to \(pK_a\), because mixing equal volumes produces equal amounts of \(\text{HA(aq)}\) and \(\text{A}^-\text{(aq)}\).
- **C.** The pH is less than \(pK_a\), because doubling the total volume decreases the \(K_a\) of \(\text{HA(aq)}\).
- **D.** The pH is less than \(pK_a\), because neutralization leaves twice as many moles of \(\text{HA(aq)}\) as the moles of \(\text{A}^-\text{(aq)}\) produced.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119426/*