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title: "A student titrates a \\(25.0\\text{ mL}\\) sample of \\(0.10\\text{ M CH}_3\\text{COOH(aq)}\\) with \\(0.10\\text{ M NaOH(aq)}\\) at \\(25\\ ^\\circ\\text{C}\\). For acetic acid, \\(K_a = 1.8 \\times 10^{-5}\\) (\\(\\text{p}K_a = 4.74\\)) at this temperature. The titration is paused when the \\(\\text{pH}\\) of the mixture is measured to be \\(5.74\\). Which of the following correctly predicts the relative concentrations of \\(\\text{CH}_3\\text{COOH(aq)}\\) and \\(\\text{CH}_3\\text{COO}^-\\text{(aq)}\\) in the solution at \\(\\text{pH} = 5.74\\), and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/121481/"
date_modified: "2026-08-23T05:04:48+00:00"
---

# A student titrates a \(25.0\text{ mL}\) sample of \(0.10\text{ M CH}_3\text{COOH(aq)}\) with \(0.10\text{ M NaOH(aq)}\) at \(25\ ^\circ\text{C}\). For acetic acid, \(K_a = 1.8 \times 10^{-5}\) (\(\text{p}K_a = 4.74\)) at this temperature. The titration is paused when the \(\text{pH}\) of the mixture is measured to be \(5.74\). Which of the following correctly predicts the relative concentrations of \(\text{CH}_3\text{COOH(aq)}\) and \(\text{CH}_3\text{COO}^-\text{(aq)}\) in the solution at \(\text{pH} = 5.74\), and provides the correct justification?

A student titrates a \(25.0\text{ mL}\) sample of \(0.10\text{ M CH}_3\text{COOH(aq)}\) with \(0.10\text{ M NaOH(aq)}\) at \(25\ ^\circ\text{C}\). For acetic acid, \(K_a = 1.8 \times 10^{-5}\) (\(\text{p}K_a = 4.74\)) at this temperature. The titration is paused when the \(\text{pH}\) of the mixture is measured to be \(5.74\). Which of the following correctly predicts the relative concentrations of \(\text{CH}_3\text{COOH(aq)}\) and \(\text{CH}_3\text{COO}^-\text{(aq)}\) in the solution at \(\text{pH} = 5.74\), and provides the correct justification?

- **A.** \([\text{CH}_3\text{COOH}] > [\text{CH}_3\text{COO}^-]\), because \(\text{pH} > \text{p}K_a\), which indicates that the majority of the acid molecules remain protonated.
- **B.** \([\text{CH}_3\text{COO}^-] > [\text{CH}_3\text{COOH}]\), because \(\text{pH} > \text{p}K_a\), which requires the ratio \(\dfrac{[\text{CH}_3\text{COO}^-]}{[\text{CH}_3\text{COOH}]} > 1\).
- **C.** \([\text{CH}_3\text{COOH}] > [\text{CH}_3\text{COO}^-]\), because the solution has \(\text{pH} < 7.00\), which indicates that the acidic form of the conjugate pair must predominate.
- **D.** \([\text{CH}_3\text{COO}^-] = [\text{CH}_3\text{COOH}]\), because the solution is within the buffer region, which ensures that equal concentrations of the weak acid and its conjugate base are maintained.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121481/*