---
title: "A student uses mass spectrometry to analyze a metal sample known to consist primarily of zirconium (\\(\\text{Zr}\\), atomic number \\(40\\)) that is suspected to be contaminated with molybdenum (\\(\\text{Mo}\\), atomic number \\(42\\)). Naturally occurring zirconium has isotopes with mass numbers \\(90\\), \\(91\\), \\(92\\), \\(94\\), and \\(96\\). Naturally occurring molybdenum has isotopes with mass numbers \\(92\\), \\(94\\), \\(95\\), \\(96\\), \\(97\\), \\(98\\), and \\(100\\). The mass spectrum data for the singly charged (\\(+1\\)) ions generated from the sample are shown in the table below.  | Mass-to-charge ratio (\\(m/z\\)) | Relative intensity | | :— | :— | | \\(90\\) | \\(51.5\\) | | \\(91\\) | \\(11.2\\) | | \\(92\\) | \\(18.5\\) | | \\(94\\) | \\(18.1\\) | | \\(95\\) | \\(2.4\\) | | \\(96\\) | \\(4.8\\) | | \\(98\\) | \\(3.6\\) |  Which of the following conclusions is best supported by the data in the table?"
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url: "https://nerd-notes.com/ubq/120167/"
date_modified: "2026-08-21T16:02:43+00:00"
---

# A student uses mass spectrometry to analyze a metal sample known to consist primarily of zirconium (\(\text{Zr}\), atomic number \(40\)) that is suspected to be contaminated with molybdenum (\(\text{Mo}\), atomic number \(42\)). Naturally occurring zirconium has isotopes with mass numbers \(90\), \(91\), \(92\), \(94\), and \(96\). Naturally occurring molybdenum has isotopes with mass numbers \(92\), \(94\), \(95\), \(96\), \(97\), \(98\), and \(100\). The mass spectrum data for the singly charged (\(+1\)) ions generated from the sample are shown in the table below.

| Mass-to-charge ratio (\(m/z\)) | Relative intensity |
| :— | :— |
| \(90\) | \(51.5\) |
| \(91\) | \(11.2\) |
| \(92\) | \(18.5\) |
| \(94\) | \(18.1\) |
| \(95\) | \(2.4\) |
| \(96\) | \(4.8\) |
| \(98\) | \(3.6\) |

Which of the following conclusions is best supported by the data in the table?

A student uses mass spectrometry to analyze a metal sample known to consist primarily of zirconium (\(\text{Zr}\), atomic number \(40\)) that is suspected to be contaminated with molybdenum (\(\text{Mo}\), atomic number \(42\)). Naturally occurring zirconium has isotopes with mass numbers \(90\), \(91\), \(92\), \(94\), and \(96\). Naturally occurring molybdenum has isotopes with mass numbers \(92\), \(94\), \(95\), \(96\), \(97\), \(98\), and \(100\). The mass spectrum data for the singly charged (\(+1\)) ions generated from the sample are shown in the table below.

| Mass-to-charge ratio (\(m/z\)) | Relative intensity |
| :--- | :--- |
| \(90\) | \(51.5\) |
| \(91\) | \(11.2\) |
| \(92\) | \(18.5\) |
| \(94\) | \(18.1\) |
| \(95\) | \(2.4\) |
| \(96\) | \(4.8\) |
| \(98\) | \(3.6\) |

Which of the following conclusions is best supported by the data in the table?

- **A.** The sample contains no molybdenum because the peak with the greatest intensity appears at \(m/z = 90\), which corresponds only to zirconium.
- **B.** The sample contains only zirconium because the peak at \(m/z = 98\) is formed by \(^{90}\text{Zr}^+\) ions that gained neutrons inside the ionization chamber.
- **C.** The signal at \(m/z = 96\) is produced exclusively by \(^{96}\text{Zr}^+\) because isotopes of different chemical elements cannot have identical mass numbers.
- **D.** The sample contains molybdenum as an impurity, and the signal at \(m/z = 96\) represents an isobaric interference where both \(^{96}\text{Zr}^+\) and \(^{96}\text{Mo}^+\) ions contribute to the peak.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120167/*