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title: "A buffer solution is prepared by mixing \\(50.0\\text{ mL}\\) of \\(0.20\\text{ M }\\text{HNO}_2\\text{(aq)}\\) with \\(50.0\\text{ mL}\\) of \\(0.20\\text{ M }\\text{NaNO}_2\\text{(aq)}\\). A student adds \\(1.0\\text{ mL}\\) of \\(0.10\\text{ M }\\text{HCl(aq)}\\) to the mixture. Which of the following best explains the effect of the added \\(\\text{HCl(aq)}\\) on the \\(\\text{pH}\\) of the solution?"
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url: "https://nerd-notes.com/ubq/121475/"
date_modified: "2026-08-23T05:04:46+00:00"
---

# A buffer solution is prepared by mixing \(50.0\text{ mL}\) of \(0.20\text{ M }\text{HNO}_2\text{(aq)}\) with \(50.0\text{ mL}\) of \(0.20\text{ M }\text{NaNO}_2\text{(aq)}\). A student adds \(1.0\text{ mL}\) of \(0.10\text{ M }\text{HCl(aq)}\) to the mixture. Which of the following best explains the effect of the added \(\text{HCl(aq)}\) on the \(\text{pH}\) of the solution?

A buffer solution is prepared by mixing \(50.0\text{ mL}\) of \(0.20\text{ M }\text{HNO}_2\text{(aq)}\) with \(50.0\text{ mL}\) of \(0.20\text{ M }\text{NaNO}_2\text{(aq)}\). A student adds \(1.0\text{ mL}\) of \(0.10\text{ M }\text{HCl(aq)}\) to the mixture. Which of the following best explains the effect of the added \(\text{HCl(aq)}\) on the \(\text{pH}\) of the solution?

- **A.** The \(\text{pH}\) decreases significantly because \(\text{HCl}\) is a strong acid that completely dissociates, leaving a high concentration of unreacted \(\text{H}^+\text{(aq)}\) ions in the solution.
- **B.** The \(\text{pH}\) decreases only slightly because the added \(\text{H}^+\text{(aq)}\) ions are consumed by reacting with \(\text{HNO}_2\text{(aq)}\) molecules to form \(\text{NO}_2^-\text{(aq)}\) ions.
- **C.** The \(\text{pH}\) decreases only slightly because the added \(\text{H}^+\text{(aq)}\) ions are consumed by reacting with \(\text{NO}_2^-\text{(aq)}\) ions to form \(\text{HNO}_2\text{(aq)}\) molecules.
- **D.** The \(\text{pH}\) decreases significantly because \(\text{Cl}^-\text{(aq)}\) ions shift the weak acid ionization equilibrium toward the products, generating additional \(\text{H}^+\text{(aq)}\) ions.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121475/*