---
title: "A rigid container holds an equimolar mixture of helium gas, \\(\\text{He(g)}\\), and argon gas, \\(\\text{Ar(g)}\\), at \\(298\\text{ K}\\). Which of the following correctly compares the average speed of the \\(\\text{He}\\) atoms to the average speed of the \\(\\text{Ar}\\) atoms, and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/119861/"
date_modified: "2026-08-21T08:16:30+00:00"
---

# A rigid container holds an equimolar mixture of helium gas, \(\text{He(g)}\), and argon gas, \(\text{Ar(g)}\), at \(298\text{ K}\). Which of the following correctly compares the average speed of the \(\text{He}\) atoms to the average speed of the \(\text{Ar}\) atoms, and provides the correct justification?

A rigid container holds an equimolar mixture of helium gas, \(\text{He(g)}\), and argon gas, \(\text{Ar(g)}\), at \(298\text{ K}\). Which of the following correctly compares the average speed of the \(\text{He}\) atoms to the average speed of the \(\text{Ar}\) atoms, and provides the correct justification?

- **A.** The average speed of \(\text{He}\) atoms is greater than that of \(\text{Ar}\) atoms because at \(298\text{ K}\) both gases have the same average kinetic energy, and \(\text{He}\) has a smaller molar mass.
- **B.** The average speed of \(\text{He}\) atoms is greater than that of \(\text{Ar}\) atoms because at \(298\text{ K}\) lighter gas particles possess a greater average kinetic energy than heavier gas particles.
- **C.** The average speed of \(\text{He}\) atoms is less than that of \(\text{Ar}\) atoms because at \(298\text{ K}\) heavier gas particles transfer more momentum during collisions to maintain pressure.
- **D.** The average speed of \(\text{He}\) atoms is equal to that of \(\text{Ar}\) atoms because at \(298\text{ K}\) temperature alone determines the speed of all ideal gas particles.

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