---
title: "The mass spectrum of a naturally occurring sample of zirconium ( \\(\\text{Zr}\\) ) is shown in the graph. Based on the mass spectrum, which of the following is the best estimate of the average atomic mass of  \\(\\text{Zr}\\) , along with the correct justification?"
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url: "https://nerd-notes.com/ubq/121410/"
date_modified: "2026-08-23T05:02:08+00:00"
---

# The mass spectrum of a naturally occurring sample of zirconium (
\(\text{Zr}\)
) is shown in the graph. Based on the mass spectrum, which of the following is the best estimate of the average atomic mass of 
\(\text{Zr}\)
, along with the correct justification?

The mass spectrum of a naturally occurring sample of zirconium (
\(\text{Zr}\)
) is shown in the graph. Based on the mass spectrum, which of the following is the best estimate of the average atomic mass of 
\(\text{Zr}\)
, along with the correct justification?

![A grayscale 2D plot representing a mass spectrum. The horizontal axis is labeled 'Mass-to-Charge Ratio (m/z)' with major tick marks and labels at 88, 90, 92, 94, 96, and 98. The vertical axis is labeled 'Relative Abundance (%)' with tick marks and labels at 0, 10, 20, 30, 40, 50, and 60. No background gridlines appear. The graph contains exactly five solid vertical line peaks located at specific integer values on the horizontal axis: a peak at m/z = 90 with a height of 51.5%; a peak at m/z = 91 with a height of 11.2%; a peak at m/z = 92 with a height of 17.1%; a peak at m/z = 94 with a height of 17.4%; and a peak at m/z = 96 with a height of 2.8%. No other peaks, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787461328-PS6ONo.jpg)

- **A.** Between \(91 \text{ amu}\) and \(92 \text{ amu}\), because the isotope with mass number \(90\) is the most abundant, but the combined presence of the heavier isotopes pulls the average above \(91 \text{ amu}\).
- **B.** Equal to \(92.6 \text{ amu}\), because the average atomic mass is calculated by taking the simple arithmetic mean of the five isotopic masses.
- **C.** Less than \(90.5 \text{ amu}\), because the isotope with mass number \(90\) accounts for more than \(50\%\) of the total atoms in the sample.
- **D.** Greater than \(93.0 \text{ amu}\), because four of the five isotopes have mass numbers greater than \(90\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121410/*