---
title: "A manufacturer lists magnesium oxide, \\(\\text{MgO}\\), as \\(40.0\\%\\) of the mass of a tablet. Any remaining material consists of inert excipients that contain no magnesium. A student obtains the following elemental-analysis results.  | Quantity | Value | |—|—:| | Mass of tablet sample | \\(2.000\\text{ g}\\) | | Mass of \\(\\text{Mg}\\) in sample | \\(0.480\\text{ g}\\) | | Molar mass of \\(\\text{Mg}\\) | \\(24.3\\text{ g/mol}\\) | | Molar mass of \\(\\text{MgO}\\) | \\(40.3\\text{ g/mol}\\) |  Which statement best reconciles the elemental-analysis result with the listed mass percent and accounts for the remaining tablet mass?"
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url: "https://nerd-notes.com/ubq/119444/"
date_modified: "2026-08-19T12:40:25+00:00"
---

# A manufacturer lists magnesium oxide, \(\text{MgO}\), as \(40.0\%\) of the mass of a tablet. Any remaining material consists of inert excipients that contain no magnesium. A student obtains the following elemental-analysis results.

| Quantity | Value |
|—|—:|
| Mass of tablet sample | \(2.000\text{ g}\) |
| Mass of \(\text{Mg}\) in sample | \(0.480\text{ g}\) |
| Molar mass of \(\text{Mg}\) | \(24.3\text{ g/mol}\) |
| Molar mass of \(\text{MgO}\) | \(40.3\text{ g/mol}\) |

Which statement best reconciles the elemental-analysis result with the listed mass percent and accounts for the remaining tablet mass?

A manufacturer lists magnesium oxide, \(\text{MgO}\), as \(40.0\%\) of the mass of a tablet. Any remaining material consists of inert excipients that contain no magnesium. A student obtains the following elemental-analysis results.

| Quantity | Value |
|---|---:|
| Mass of tablet sample | \(2.000\text{ g}\) |
| Mass of \(\text{Mg}\) in sample | \(0.480\text{ g}\) |
| Molar mass of \(\text{Mg}\) | \(24.3\text{ g/mol}\) |
| Molar mass of \(\text{MgO}\) | \(40.3\text{ g/mol}\) |

Which statement best reconciles the elemental-analysis result with the listed mass percent and accounts for the remaining tablet mass?

- **A.** The results are inconsistent, and the tablet contains only \(24.0\%\) \(\text{MgO}\) by mass, because the measured mass percent of \(\text{Mg}\) is equal to the mass percent of \(\text{MgO}\).
- **B.** The results are inconsistent, and the tablet contains about \(14.5\%\) \(\text{MgO}\) by mass, because the mass of \(\text{Mg}\) should be multiplied by \(\dfrac{24.3}{40.3}\) to obtain the mass of \(\text{MgO}\).
- **C.** The results are consistent, and \(76.0\%\) of the tablet is inert excipient, because every part of the sample mass not measured as \(\text{Mg}\) must be inactive material.
- **D.** The results are consistent, and about \(60.2\%\) of the tablet is inert excipient, because \(0.480\text{ g}\) of \(\text{Mg}\) corresponds to about \(0.796\text{ g}\) of \(\text{MgO}\), or \(39.8\%\) of the sample mass.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119444/*