---
title: "A student measures the pressure exerted by \\(1.00\\text{ mol}\\) of \\(\\text{CH}_4\\text{(g)}\\) and \\(1.00\\text{ mol}\\) of \\(\\text{NH}_3\\text{(g)}\\) in separate, identical \\(1.00\\text{ L}\\) rigid containers at \\(250\\text{ K}\\). Under these conditions, the measured pressure for each gas is less than the pressure predicted by the ideal gas law, and the measured pressure of \\(\\text{NH}_3\\text{(g)}\\) is significantly lower than that of \\(\\text{CH}_4\\text{(g)}\\). Which of the following statements best justifies the observed difference in pressure between the two gases?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/123659/"
date_modified: "2026-09-28T12:01:54+00:00"
---

# A student measures the pressure exerted by \(1.00\text{ mol}\) of \(\text{CH}_4\text{(g)}\) and \(1.00\text{ mol}\) of \(\text{NH}_3\text{(g)}\) in separate, identical \(1.00\text{ L}\) rigid containers at \(250\text{ K}\). Under these conditions, the measured pressure for each gas is less than the pressure predicted by the ideal gas law, and the measured pressure of \(\text{NH}_3\text{(g)}\) is significantly lower than that of \(\text{CH}_4\text{(g)}\). Which of the following statements best justifies the observed difference in pressure between the two gases?

A student measures the pressure exerted by \(1.00\text{ mol}\) of \(\text{CH}_4\text{(g)}\) and \(1.00\text{ mol}\) of \(\text{NH}_3\text{(g)}\) in separate, identical \(1.00\text{ L}\) rigid containers at \(250\text{ K}\). Under these conditions, the measured pressure for each gas is less than the pressure predicted by the ideal gas law, and the measured pressure of \(\text{NH}_3\text{(g)}\) is significantly lower than that of \(\text{CH}_4\text{(g)}\). Which of the following statements best justifies the observed difference in pressure between the two gases?

- **A.** The measured pressure of \(\text{NH}_3\text{(g)}\) is lower because \(\text{NH}_3\) molecules experience stronger intermolecular attractions (dipole-dipole forces and hydrogen bonding) than the nonpolar \(\text{CH}_4\) molecules, which reduces the force of wall collisions to a greater extent.
- **B.** The measured pressure of \(\text{NH}_3\text{(g)}\) is lower because the finite volume occupied by \(\text{NH}_3\) molecules reduces the free volume available in the container to a greater extent than that of \(\text{CH}_4\) molecules.
- **C.** The measured pressure of \(\text{NH}_3\text{(g)}\) is lower because \(\text{NH}_3\) molecules have a greater molar mass than \(\text{CH}_4\) molecules, resulting in a lower average kinetic energy and weaker wall collisions at \(250\text{ K}\).
- **D.** The measured pressure of \(\text{NH}_3\text{(g)}\) is lower because \(\text{NH}_3\) molecules are significantly more polarizable than \(\text{CH}_4\) molecules, leading to much stronger London dispersion forces.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123659/*