---
title: "In a gas-recovery study, a student places separate samples containing identical numbers of gas molecules into identical rigid vessels at the same temperature. The vessels are maintained at high pressure, and both samples remain single phases. The student calculates the compressibility factor, defined as \\(Z=\\dfrac{PV}{nRT}\\). For an ideal gas, \\(Z=1\\).  | Gas | Molecular description | Measured \\(Z\\) | |—–|———————–|—————-| | \\(\\text{CH}_4\\) | Tetrahedral and nonpolar | \\(0.96\\) | | \\(\\text{SO}_2\\) | Bent and polar | \\(0.72\\) |  Which choice ranks the gases from greatest to least magnitude of deviation from ideal behavior and best explains the ranking?"
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url: "https://nerd-notes.com/ubq/119498/"
date_modified: "2026-08-19T12:40:48+00:00"
---

# In a gas-recovery study, a student places separate samples containing identical numbers of gas molecules into identical rigid vessels at the same temperature. The vessels are maintained at high pressure, and both samples remain single phases. The student calculates the compressibility factor, defined as \(Z=\dfrac{PV}{nRT}\). For an ideal gas, \(Z=1\).

| Gas | Molecular description | Measured \(Z\) |
|—–|———————–|—————-|
| \(\text{CH}_4\) | Tetrahedral and nonpolar | \(0.96\) |
| \(\text{SO}_2\) | Bent and polar | \(0.72\) |

Which choice ranks the gases from greatest to least magnitude of deviation from ideal behavior and best explains the ranking?

In a gas-recovery study, a student places separate samples containing identical numbers of gas molecules into identical rigid vessels at the same temperature. The vessels are maintained at high pressure, and both samples remain single phases. The student calculates the compressibility factor, defined as \(Z=\dfrac{PV}{nRT}\). For an ideal gas, \(Z=1\).

| Gas | Molecular description | Measured \(Z\) |
|-----|-----------------------|----------------|
| \(\text{CH}_4\) | Tetrahedral and nonpolar | \(0.96\) |
| \(\text{SO}_2\) | Bent and polar | \(0.72\) |

Which choice ranks the gases from greatest to least magnitude of deviation from ideal behavior and best explains the ranking?

- **A.** \(\text{CH}_4 > \text{SO}_2\), because a value of \(Z\) closer to 1 indicates a larger fractional pressure decrease caused by intermolecular attractions.
- **B.** \(\text{CH}_4 > \text{SO}_2\), because the lower molar mass of \(\text{CH}_4\) gives its molecules a greater average speed, which produces a greater departure from ideal behavior.
- **C.** \(\text{SO}_2 > \text{CH}_4\), because the larger volume occupied by individual \(\text{SO}_2\) molecules lowers the measured pressure below the ideal pressure.
- **D.** \(\text{SO}_2 > \text{CH}_4\), because dipole-dipole attractions between \(\text{SO}_2\) molecules reduce momentum transfer to the vessel walls more strongly than the dispersion forces between \(\text{CH}_4\) molecules do.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119498/*