---
title: "A student titrates a sample of an unknown monoprotic weak acid with standard \\(0.10 \\text{ M NaOH(aq)}\\) using a pH meter and generates the titration curve shown. The student plans to repeat the experiment using a chemical indicator to signal the endpoint instead of using a pH meter. Based on the titration curve, which of the following correctly identifies the volume of \\(\\text{NaOH(aq)}\\) required to reach the equivalence point and selects the most appropriate indicator for the titration?"
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url: "https://nerd-notes.com/ubq/119242/"
date_modified: "2026-08-19T12:39:31+00:00"
---

# A student titrates a sample of an unknown monoprotic weak acid with standard \(0.10 \text{ M NaOH(aq)}\) using a pH meter and generates the titration curve shown. The student plans to repeat the experiment using a chemical indicator to signal the endpoint instead of using a pH meter. Based on the titration curve, which of the following correctly identifies the volume of \(\text{NaOH(aq)}\) required to reach the equivalence point and selects the most appropriate indicator for the titration?

A student titrates a sample of an unknown monoprotic weak acid with standard \(0.10 \text{ M NaOH(aq)}\) using a pH meter and generates the titration curve shown. The student plans to repeat the experiment using a chemical indicator to signal the endpoint instead of using a pH meter. Based on the titration curve, which of the following correctly identifies the volume of \(\text{NaOH(aq)}\) required to reach the equivalence point and selects the most appropriate indicator for the titration?

![A titration curve plotted on a two-dimensional grid with visible dashed gridlines. The horizontal x-axis is labeled 'Volume of NaOH added (mL)' with numerical tick marks at 0, 10, 20, 25, 30, 40, and 50. The vertical y-axis is labeled 'pH' with numerical tick marks at 0, 2, 4, 6, 8, 10, 12, and 14. A single solid black curve starts at coordinate (0, 3.0), gradually rises through (10, 4.2) and (12.5, 4.7) to (20, 5.5). The curve then rises steeply and nearly vertically from (24, 6.0) through an inflection point at coordinate (25.0, 8.5) up to (26, 11.0). Above pH 11, the curve flattens rightward, passing through (30, 12.0) and ending at (50, 12.5). No other curves, labels, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787143171-jEtWpJ.jpg)

- **A.** Volume: \(25.0 \text{ mL}\); Indicator: Phenolphthalein (pH range 8.2–10.0), because its color-change range coincides with the steep pH jump surrounding the equivalence point.
- **B.** Volume: \(12.5 \text{ mL}\); Indicator: Methyl red (pH range 4.4–6.2), because the equivalence point occurs where the pH changes most gradually in the buffer region.
- **C.** Volume: \(25.0 \text{ mL}\); Indicator: Methyl red (pH range 4.4–6.2), because its color-change range matches the initial pH range of the weak acid solution.
- **D.** Volume: \(50.0 \text{ mL}\); Indicator: Phenolphthalein (pH range 8.2–10.0), because the equivalence point is reached when the solution pH levels off at its maximum value.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119242/*