---
title: "A student standardizes an unknown solid diprotic acid, \\(\\text{H}_2\\text{A}\\), by dissolving a sample in distilled water to prepare a stock solution and titrating an aliquot with standardized \\(\\text{NaOH(aq)}\\) to the second equivalence point according to the following equation:  \\[ \\text{H}_2\\text{A(aq)} + 2\\,\\text{NaOH(aq)} \\rightarrow \\text{Na}_2\\text{A(aq)} + 2\\,\\text{H}_2\\text{O(l)} \\]  The student records the laboratory data shown in the table below.  | Measurement | Value | | :— | :— | | Mass of unknown \\(\\text{H}_2\\text{A}\\) dissolved | \\(1.800 \\text{ g}\\) | | Total volume of prepared stock solution | \\(250.0 \\text{ mL}\\) | | Volume of stock solution titrated (aliquot) | \\(50.00 \\text{ mL}\\) | | Concentration of standardized \\(\\text{NaOH(aq)}\\) | \\(0.100 \\text{ M}\\) | | Initial \\(\\text{NaOH}\\) buret reading | \\(3.50 \\text{ mL}\\) | | Final \\(\\text{NaOH}\\) buret reading at second equivalence point | \\(43.50 \\text{ mL}\\) |  Based on the data collected, what is the molar mass of the unknown diprotic acid?"
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url: "https://nerd-notes.com/ubq/123737/"
date_modified: "2026-09-28T12:02:15+00:00"
---

# A student standardizes an unknown solid diprotic acid, \(\text{H}_2\text{A}\), by dissolving a sample in distilled water to prepare a stock solution and titrating an aliquot with standardized \(\text{NaOH(aq)}\) to the second equivalence point according to the following equation:

\[ \text{H}_2\text{A(aq)} + 2\,\text{NaOH(aq)} \rightarrow \text{Na}_2\text{A(aq)} + 2\,\text{H}_2\text{O(l)} \]

The student records the laboratory data shown in the table below.

| Measurement | Value |
| :— | :— |
| Mass of unknown \(\text{H}_2\text{A}\) dissolved | \(1.800 \text{ g}\) |
| Total volume of prepared stock solution | \(250.0 \text{ mL}\) |
| Volume of stock solution titrated (aliquot) | \(50.00 \text{ mL}\) |
| Concentration of standardized \(\text{NaOH(aq)}\) | \(0.100 \text{ M}\) |
| Initial \(\text{NaOH}\) buret reading | \(3.50 \text{ mL}\) |
| Final \(\text{NaOH}\) buret reading at second equivalence point | \(43.50 \text{ mL}\) |

Based on the data collected, what is the molar mass of the unknown diprotic acid?

A student standardizes an unknown solid diprotic acid, \(\text{H}_2\text{A}\), by dissolving a sample in distilled water to prepare a stock solution and titrating an aliquot with standardized \(\text{NaOH(aq)}\) to the second equivalence point according to the following equation:

\[ \text{H}_2\text{A(aq)} + 2\,\text{NaOH(aq)} \rightarrow \text{Na}_2\text{A(aq)} + 2\,\text{H}_2\text{O(l)} \]

The student records the laboratory data shown in the table below.

| Measurement | Value |
| :--- | :--- |
| Mass of unknown \(\text{H}_2\text{A}\) dissolved | \(1.800 \text{ g}\) |
| Total volume of prepared stock solution | \(250.0 \text{ mL}\) |
| Volume of stock solution titrated (aliquot) | \(50.00 \text{ mL}\) |
| Concentration of standardized \(\text{NaOH(aq)}\) | \(0.100 \text{ M}\) |
| Initial \(\text{NaOH}\) buret reading | \(3.50 \text{ mL}\) |
| Final \(\text{NaOH}\) buret reading at second equivalence point | \(43.50 \text{ mL}\) |

Based on the data collected, what is the molar mass of the unknown diprotic acid?

- **A.** \(180 \text{ g/mol}\)
- **B.** \(450 \text{ g/mol}\)
- **C.** \(900 \text{ g/mol}\)
- **D.** \(1800 \text{ g/mol}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123737/*