---
title: "A student investigates the thermal decomposition of gas-phase nitrogen dioxide according to the reaction \\(\\text{2 NO}_2\\text{(g)} \\rightarrow \\text{2 NO(g)} + \\text{O}_2\\text{(g)}\\). The student measures the concentration of \\(\\text{NO}_2\\text{(g)}\\) as a function of time at a constant temperature and constructs three integrated rate law plots, as shown below. Which of the following best identifies the order of the reaction with respect to \\(\\text{NO}_2\\) and provides the correct justification?"
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date_modified: "2026-08-19T12:39:35+00:00"
---

# A student investigates the thermal decomposition of gas-phase nitrogen dioxide according to the reaction \(\text{2 NO}_2\text{(g)} \rightarrow \text{2 NO(g)} + \text{O}_2\text{(g)}\). The student measures the concentration of \(\text{NO}_2\text{(g)}\) as a function of time at a constant temperature and constructs three integrated rate law plots, as shown below. Which of the following best identifies the order of the reaction with respect to \(\text{NO}_2\) and provides the correct justification?

A student investigates the thermal decomposition of gas-phase nitrogen dioxide according to the reaction \(\text{2 NO}_2\text{(g)} \rightarrow \text{2 NO(g)} + \text{O}_2\text{(g)}\). The student measures the concentration of \(\text{NO}_2\text{(g)}\) as a function of time at a constant temperature and constructs three integrated rate law plots, as shown below. Which of the following best identifies the order of the reaction with respect to \(\text{NO}_2\) and provides the correct justification?

![Three separate coordinate axes arranged horizontally labeled Plot 1, Plot 2, and Plot 3. Each plot has a horizontal axis labeled time (s). Plot 1 has a vertical axis labeled [NO2] (M) and depicts a curve that decreases non-linearly from top-left to bottom-right, concave upward. Plot 2 has a vertical axis labeled ln[NO2] and depicts a curve that decreases non-linearly from top-left to bottom-right, concave upward. Plot 3 has a vertical axis labeled 1/[NO2] (M^-1) and depicts a straight line with a positive slope starting above zero on the vertical axis and extending toward the top-right. All axes are drawn with plain black lines and no background gridlines. No other text, labels, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787143174-LWjpFA.jpg)

- **A.** Second order, because the plot of \(1/[\text{NO}_2]\) versus time is linear.
- **B.** First order, because the plot of \(\ln[\text{NO}_2]\) versus time is linear.
- **C.** Zero order, because the plot of \([\text{NO}_2]\) versus time shows a continuous decrease in concentration.
- **D.** First order, because the plot of \(1/[\text{NO}_2]\) versus time has a positive slope.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119266/*