---
title: "A rigid \\(10.0\\text{ L}\\) container holds an equimolar mixture of three gases at \\(298\\text{ K}\\), as summarized in the table below.  | Gas | Molar mass (\\(\\text{g/mol}\\)) | | :— | :— | | \\(\\text{CH}_4\\) | \\(16.04\\) | | \\(\\text{O}_2\\) | \\(32.00\\) | | \\(\\text{SO}_2\\) | \\(64.07\\) |  Which of the following lists the gases in order of decreasing average molecular speed, and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/119574/"
date_modified: "2026-08-21T06:53:56+00:00"
---

# A rigid \(10.0\text{ L}\) container holds an equimolar mixture of three gases at \(298\text{ K}\), as summarized in the table below.

| Gas | Molar mass (\(\text{g/mol}\)) |
| :— | :— |
| \(\text{CH}_4\) | \(16.04\) |
| \(\text{O}_2\) | \(32.00\) |
| \(\text{SO}_2\) | \(64.07\) |

Which of the following lists the gases in order of decreasing average molecular speed, and provides the correct justification?

A rigid \(10.0\text{ L}\) container holds an equimolar mixture of three gases at \(298\text{ K}\), as summarized in the table below.

| Gas | Molar mass (\(\text{g/mol}\)) |
| :--- | :--- |
| \(\text{CH}_4\) | \(16.04\) |
| \(\text{O}_2\) | \(32.00\) |
| \(\text{SO}_2\) | \(64.07\) |

Which of the following lists the gases in order of decreasing average molecular speed, and provides the correct justification?

- **A.** \(\text{SO}_2 > \text{O}_2 > \text{CH}_4\), because at a given temperature, molecules with greater mass possess greater average kinetic energy and therefore travel at higher speeds.
- **B.** \(\text{SO}_2 > \text{O}_2 > \text{CH}_4\), because molecules with greater molar mass exert stronger attractive forces on one another that accelerate them between collisions.
- **C.** \(\text{CH}_4 > \text{O}_2 > \text{SO}_2\), because molecules with smaller molar mass absorb more thermal energy per particle, giving them greater average kinetic energy.
- **D.** \(\text{CH}_4 > \text{O}_2 > \text{SO}_2\), because at the same temperature all three gases have the same average kinetic energy, so lighter molecules must move with greater average speed.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119574/*