---
title: "A student investigates the gas-phase reaction between nitrogen dioxide and carbon monoxide in a pollution-chemistry study.  \\[ \\text{NO}_2\\text{(g)}+\\text{CO}\\text{(g)}\\rightarrow \\text{NO}\\text{(g)}+\\text{CO}_2\\text{(g)} \\]  The student obtains the following initial-rate data at \\(300\\ \\text{K}\\).  | Trial | \\([\\text{NO}_2]\\) | \\([\\text{CO}]\\) | Initial rate | |—|—|—|—| | \\(1\\) | \\(0.010\\ \\text{M}\\) | \\(0.010\\ \\text{M}\\) | \\(2.0\\times10^{-5}\\ \\text{M s}^{-1}\\) | | \\(2\\) | \\(0.020\\ \\text{M}\\) | \\(0.010\\ \\text{M}\\) | \\(8.0\\times10^{-5}\\ \\text{M s}^{-1}\\) | | \\(3\\) | \\(0.020\\ \\text{M}\\) | \\(0.020\\ \\text{M}\\) | \\(8.0\\times10^{-5}\\ \\text{M s}^{-1}\\) |  A proposed mechanism and estimated forward activation energies are shown below.  | Step | Elementary reaction | Relative rate | \\(E_{a,\\text{forward}}\\) | |—|—|—|—| | \\(1\\) | \\(2\\text{NO}_2\\text{(g)}\\rightarrow\\text{NO}_3\\text{(g)}+\\text{NO}\\text{(g)}\\) | Slow | \\(75\\ \\text{kJ mol}^{-1}\\) | | \\(2\\) | \\(\\text{NO}_3\\text{(g)}+\\text{CO}\\text{(g)}\\rightarrow\\text{NO}_2\\text{(g)}+\\text{CO}_2\\text{(g)}\\) | Fast | \\(25\\ \\text{kJ mol}^{-1}\\) |  An Arrhenius plot constructed from additional trials gives an apparent activation energy of \\(75\\ \\text{kJ mol}^{-1}\\). Which statement best evaluates whether the proposed mechanism is consistent with the experimental kinetic data?"
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url: "https://nerd-notes.com/ubq/120098/"
date_modified: "2026-08-21T08:41:35+00:00"
---

# A student investigates the gas-phase reaction between nitrogen dioxide and carbon monoxide in a pollution-chemistry study.

\[
\text{NO}_2\text{(g)}+\text{CO}\text{(g)}\rightarrow \text{NO}\text{(g)}+\text{CO}_2\text{(g)}
\]

The student obtains the following initial-rate data at \(300\ \text{K}\).

| Trial | \([\text{NO}_2]\) | \([\text{CO}]\) | Initial rate |
|—|—|—|—|
| \(1\) | \(0.010\ \text{M}\) | \(0.010\ \text{M}\) | \(2.0\times10^{-5}\ \text{M s}^{-1}\) |
| \(2\) | \(0.020\ \text{M}\) | \(0.010\ \text{M}\) | \(8.0\times10^{-5}\ \text{M s}^{-1}\) |
| \(3\) | \(0.020\ \text{M}\) | \(0.020\ \text{M}\) | \(8.0\times10^{-5}\ \text{M s}^{-1}\) |

A proposed mechanism and estimated forward activation energies are shown below.

| Step | Elementary reaction | Relative rate | \(E_{a,\text{forward}}\) |
|—|—|—|—|
| \(1\) | \(2\text{NO}_2\text{(g)}\rightarrow\text{NO}_3\text{(g)}+\text{NO}\text{(g)}\) | Slow | \(75\ \text{kJ mol}^{-1}\) |
| \(2\) | \(\text{NO}_3\text{(g)}+\text{CO}\text{(g)}\rightarrow\text{NO}_2\text{(g)}+\text{CO}_2\text{(g)}\) | Fast | \(25\ \text{kJ mol}^{-1}\) |

An Arrhenius plot constructed from additional trials gives an apparent activation energy of \(75\ \text{kJ mol}^{-1}\). Which statement best evaluates whether the proposed mechanism is consistent with the experimental kinetic data?

A student investigates the gas-phase reaction between nitrogen dioxide and carbon monoxide in a pollution-chemistry study.

\[
\text{NO}_2\text{(g)}+\text{CO}\text{(g)}\rightarrow \text{NO}\text{(g)}+\text{CO}_2\text{(g)}
\]

The student obtains the following initial-rate data at \(300\ \text{K}\).

| Trial | \([\text{NO}_2]\) | \([\text{CO}]\) | Initial rate |
|---|---|---|---|
| \(1\) | \(0.010\ \text{M}\) | \(0.010\ \text{M}\) | \(2.0\times10^{-5}\ \text{M s}^{-1}\) |
| \(2\) | \(0.020\ \text{M}\) | \(0.010\ \text{M}\) | \(8.0\times10^{-5}\ \text{M s}^{-1}\) |
| \(3\) | \(0.020\ \text{M}\) | \(0.020\ \text{M}\) | \(8.0\times10^{-5}\ \text{M s}^{-1}\) |

A proposed mechanism and estimated forward activation energies are shown below.

| Step | Elementary reaction | Relative rate | \(E_{a,\text{forward}}\) |
|---|---|---|---|
| \(1\) | \(2\text{NO}_2\text{(g)}\rightarrow\text{NO}_3\text{(g)}+\text{NO}\text{(g)}\) | Slow | \(75\ \text{kJ mol}^{-1}\) |
| \(2\) | \(\text{NO}_3\text{(g)}+\text{CO}\text{(g)}\rightarrow\text{NO}_2\text{(g)}+\text{CO}_2\text{(g)}\) | Fast | \(25\ \text{kJ mol}^{-1}\) |

An Arrhenius plot constructed from additional trials gives an apparent activation energy of \(75\ \text{kJ mol}^{-1}\). Which statement best evaluates whether the proposed mechanism is consistent with the experimental kinetic data?

- **A.** The proposed mechanism is not consistent with the data, because the overall reaction contains one molecule each of \(\text{NO}_2\) and \(\text{CO}\) and therefore requires \(\text{rate}=k[\text{NO}_2][\text{CO}]\).
- **B.** The proposed mechanism is not consistent with the data, because the apparent activation energy of a two-step mechanism must be \(75\ \text{kJ mol}^{-1}+25\ \text{kJ mol}^{-1}=100\ \text{kJ mol}^{-1}\).
- **C.** The proposed mechanism is consistent with the data, because the slow first step predicts \(\text{rate}=k_1[\text{NO}_2]^2\), and the measured \(E_a=75\ \text{kJ mol}^{-1}\) is the positive enthalpy change of step \(1\), which makes that step slow.
- **D.** The proposed mechanism is consistent with the data, because the slow elementary step predicts \(\text{rate}=k_1[\text{NO}_2]^2\), which matches the observed concentration dependence, and the apparent \(E_a\) matches the estimated \(75\ \text{kJ mol}^{-1}\) activation barrier for that step.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120098/*