---
title: "A student injects a sample of colorless \\(\\text{N}_2\\text{O}_4\\text{(g)}\\) into an evacuated, sealed rigid container at a constant temperature. Over time, brown \\(\\text{NO}_2\\text{(g)}\\) forms according to the reaction \\(\\text{N}_2\\text{O}_4\\text{(g)} \\rightleftharpoons 2\\text{NO}_2\\text{(g)}\\). After several minutes, the intensity of the brown color inside the container remains constant. Which of the following best describes the state of the system after the brown color stops changing, and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/119216/"
date_modified: "2026-08-19T12:39:24+00:00"
---

# A student injects a sample of colorless \(\text{N}_2\text{O}_4\text{(g)}\) into an evacuated, sealed rigid container at a constant temperature. Over time, brown \(\text{NO}_2\text{(g)}\) forms according to the reaction \(\text{N}_2\text{O}_4\text{(g)} \rightleftharpoons 2\text{NO}_2\text{(g)}\). After several minutes, the intensity of the brown color inside the container remains constant. Which of the following best describes the state of the system after the brown color stops changing, and provides the correct justification?

A student injects a sample of colorless \(\text{N}_2\text{O}_4\text{(g)}\) into an evacuated, sealed rigid container at a constant temperature. Over time, brown \(\text{NO}_2\text{(g)}\) forms according to the reaction \(\text{N}_2\text{O}_4\text{(g)} \rightleftharpoons 2\text{NO}_2\text{(g)}\). After several minutes, the intensity of the brown color inside the container remains constant. Which of the following best describes the state of the system after the brown color stops changing, and provides the correct justification?

- **A.** The reaction has stopped because all of the \(\text{N}_2\text{O}_4\text{(g)}\) has been converted into \(\text{NO}_2\text{(g)}\).
- **B.** The system has reached dynamic equilibrium because the concentration of \(\text{N}_2\text{O}_4\text{(g)}\) is equal to the concentration of \(\text{NO}_2\text{(g)}\).
- **C.** The system has reached dynamic equilibrium because the rate of the forward reaction equals the rate of the reverse reaction.
- **D.** The reaction has stopped because the rates of both the forward and reverse reactions have decreased to zero.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119216/*