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title: "A student titrates a \\(25.0 \\text{ mL}\\) sample of \\(0.10 \\text{ M HA(aq)}\\) (a weak monoprotic acid) with \\(0.10 \\text{ M NaOH(aq)}\\). At a point during the titration before the equivalence point is reached, the \\(\\text{pH}\\) of the mixture is measured to be \\(\\text{pH} = \\text{p}K_a – 1.00\\), where \\(\\text{p}K_a\\) is the negative logarithm of the acid dissociation constant of \\(\\text{HA}\\). What fraction of the initial amount of \\(\\text{HA}\\) remains unreacted in the solution at this point?"
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url: "https://nerd-notes.com/ubq/123788/"
date_modified: "2026-09-28T12:30:18+00:00"
---

# A student titrates a \(25.0 \text{ mL}\) sample of \(0.10 \text{ M HA(aq)}\) (a weak monoprotic acid) with \(0.10 \text{ M NaOH(aq)}\). At a point during the titration before the equivalence point is reached, the \(\text{pH}\) of the mixture is measured to be \(\text{pH} = \text{p}K_a – 1.00\), where \(\text{p}K_a\) is the negative logarithm of the acid dissociation constant of \(\text{HA}\). What fraction of the initial amount of \(\text{HA}\) remains unreacted in the solution at this point?

A student titrates a \(25.0 \text{ mL}\) sample of \(0.10 \text{ M HA(aq)}\) (a weak monoprotic acid) with \(0.10 \text{ M NaOH(aq)}\). At a point during the titration before the equivalence point is reached, the \(\text{pH}\) of the mixture is measured to be \(\text{pH} = \text{p}K_a - 1.00\), where \(\text{p}K_a\) is the negative logarithm of the acid dissociation constant of \(\text{HA}\). What fraction of the initial amount of \(\text{HA}\) remains unreacted in the solution at this point?

- **A.** \(\dfrac{1}{11}\)
- **B.** \(\dfrac{1}{10}\)
- **C.** \(\dfrac{9}{10}\)
- **D.** \(\dfrac{10}{11}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123788/*