---
title: "A student prepares two different buffer solutions at \\(25^\\circ\\text{C}\\) using nitrous acid, \\(\\text{HNO}_2\\), and sodium nitrite, \\(\\text{NaNO}_2\\), as summarized in the table below.  | Buffer solution | Volume (mL) | \\([\\text{HNO}_2]\\) (M) | \\([\\text{NaNO}_2]\\) (M) | |—|—|—|—| | 1 | \\(100.0\\) | \\(0.50\\) | \\(0.50\\) | | 2 | \\(100.0\\) | \\(0.050\\) | \\(0.050\\) |  To a separate \\(100.0\\text{ mL}\\) sample of each buffer solution, the student adds \\(1.0\\text{ mmol}\\) of \\(\\text{HCl(aq)}\\) with negligible change in volume. Which of the following correctly compares the initial \\(\\text{pH}\\) of the two buffers and the magnitude of the \\(\\text{pH}\\) change, \\(|\\Delta\\text{pH}|\\), resulting from the addition of the \\(\\text{HCl(aq)}\\)?"
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url: "https://nerd-notes.com/ubq/123792/"
date_modified: "2026-09-28T12:30:19+00:00"
---

# A student prepares two different buffer solutions at \(25^\circ\text{C}\) using nitrous acid, \(\text{HNO}_2\), and sodium nitrite, \(\text{NaNO}_2\), as summarized in the table below.

| Buffer solution | Volume (mL) | \([\text{HNO}_2]\) (M) | \([\text{NaNO}_2]\) (M) |
|—|—|—|—|
| 1 | \(100.0\) | \(0.50\) | \(0.50\) |
| 2 | \(100.0\) | \(0.050\) | \(0.050\) |

To a separate \(100.0\text{ mL}\) sample of each buffer solution, the student adds \(1.0\text{ mmol}\) of \(\text{HCl(aq)}\) with negligible change in volume. Which of the following correctly compares the initial \(\text{pH}\) of the two buffers and the magnitude of the \(\text{pH}\) change, \(|\Delta\text{pH}|\), resulting from the addition of the \(\text{HCl(aq)}\)?

A student prepares two different buffer solutions at \(25^\circ\text{C}\) using nitrous acid, \(\text{HNO}_2\), and sodium nitrite, \(\text{NaNO}_2\), as summarized in the table below.

| Buffer solution | Volume (mL) | \([\text{HNO}_2]\) (M) | \([\text{NaNO}_2]\) (M) |
|---|---|---|---|
| 1 | \(100.0\) | \(0.50\) | \(0.50\) |
| 2 | \(100.0\) | \(0.050\) | \(0.050\) |

To a separate \(100.0\text{ mL}\) sample of each buffer solution, the student adds \(1.0\text{ mmol}\) of \(\text{HCl(aq)}\) with negligible change in volume. Which of the following correctly compares the initial \(\text{pH}\) of the two buffers and the magnitude of the \(\text{pH}\) change, \(|\Delta\text{pH}|\), resulting from the addition of the \(\text{HCl(aq)}\)?

- **A.** \(\text{pH}_{\text{Buffer 1}} < \text{pH}_{\text{Buffer 2}}\), and \(|\Delta\text{pH}|_{\text{Buffer 1}} > |\Delta\text{pH}|_{\text{Buffer 2}}\) because the higher concentration of \(\text{HNO}_2\) in Buffer 1 makes it initially more acidic and less resistant to added acid.
- **B.** \(\text{pH}_{\text{Buffer 1}} = \text{pH}_{\text{Buffer 2}}\), and \(|\Delta\text{pH}|_{\text{Buffer 1}} > |\Delta\text{pH}|_{\text{Buffer 2}}\) because the higher concentration of \(\text{NO}_2^-\) in Buffer 1 leads to more collisions with added \(\text{H}^+\) ions, driving a greater shift in equilibrium.
- **C.** \(\text{pH}_{\text{Buffer 1}} = \text{pH}_{\text{Buffer 2}}\), and \(|\Delta\text{pH}|_{\text{Buffer 1}} < |\Delta\text{pH}|_{\text{Buffer 2}}\) because the addition of \(\text{HCl}\) causes a smaller fractional change in the \([\text{NO}_2^-]/[\text{HNO}_2]\) ratio in Buffer 1 than in Buffer 2.
- **D.** \(\text{pH}_{\text{Buffer 1}} = \text{pH}_{\text{Buffer 2}}\), and \(|\Delta\text{pH}|_{\text{Buffer 1}} = |\Delta\text{pH}|_{\text{Buffer 2}}\) because both solutions have the same initial ratio of conjugate base to weak acid, resulting in equal buffering capacities.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123792/*