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title: "A student investigates the gas-phase decomposition of nitrogen dioxide at a constant temperature of \\(500\\text{ K}\\) according to the following equation:  \\[ 2\\,\\text{NO}_2\\text{(g)} \\rightarrow 2\\,\\text{NO(g)} + \\text{O}_2\\text{(g)} \\]  The student measures the concentration of \\(\\text{NO}_2\\text{(g)}\\) at various times during the reaction and collects the data shown in the table below.  | Time (\\(\\text{s}\\)) | \\([\\text{NO}_2]\\) (\\(\\text{M}\\)) | |—|—| | \\(0\\) | \\(0.80\\) | | \\(100\\) | \\(0.40\\) | | \\(300\\) | \\(0.20\\) | | \\(700\\) | \\(0.10\\) |  Which of the following claims is correct regarding the order of the reaction with respect to \\(\\text{NO}_2\\), and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/123621/"
date_modified: "2026-09-28T12:01:48+00:00"
---

# A student investigates the gas-phase decomposition of nitrogen dioxide at a constant temperature of \(500\text{ K}\) according to the following equation:

\[ 2\,\text{NO}_2\text{(g)} \rightarrow 2\,\text{NO(g)} + \text{O}_2\text{(g)} \]

The student measures the concentration of \(\text{NO}_2\text{(g)}\) at various times during the reaction and collects the data shown in the table below.

| Time (\(\text{s}\)) | \([\text{NO}_2]\) (\(\text{M}\)) |
|—|—|
| \(0\) | \(0.80\) |
| \(100\) | \(0.40\) |
| \(300\) | \(0.20\) |
| \(700\) | \(0.10\) |

Which of the following claims is correct regarding the order of the reaction with respect to \(\text{NO}_2\), and provides the correct justification?

A student investigates the gas-phase decomposition of nitrogen dioxide at a constant temperature of \(500\text{ K}\) according to the following equation:

\[ 2\,\text{NO}_2\text{(g)} \rightarrow 2\,\text{NO(g)} + \text{O}_2\text{(g)} \]

The student measures the concentration of \(\text{NO}_2\text{(g)}\) at various times during the reaction and collects the data shown in the table below.

| Time (\(\text{s}\)) | \([\text{NO}_2]\) (\(\text{M}\)) |
|---|---|
| \(0\) | \(0.80\) |
| \(100\) | \(0.40\) |
| \(300\) | \(0.20\) |
| \(700\) | \(0.10\) |

Which of the following claims is correct regarding the order of the reaction with respect to \(\text{NO}_2\), and provides the correct justification?

- **A.** The reaction is first order because the rate of disappearance of \(\text{NO}_2\) decreases as the concentration of \(\text{NO}_2\) decreases.
- **B.** The reaction is first order because the time required to consume half of the remaining \(\text{NO}_2\) increases by a factor of \(2\) for each consecutive half-life.
- **C.** The reaction is second order because each successive half-life doubles as the concentration of \(\text{NO}_2\) is halved, which is consistent with \(t_{1/2} = \dfrac{1}{k[\text{NO}_2]_0}\).
- **D.** The reaction is second order because the concentration of \(\text{NO}_2\) decreases by equal amounts over equal successive time intervals.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123621/*