---
title: "A student investigates the rate of the gas-phase decomposition of nitrogen dioxide represented by the equation below:  \\[ 2\\text{NO}_2\\text{(g)} \\rightarrow 2\\text{NO(g)} + \\text{O}_2\\text{(g)} \\]  When the temperature of the reaction vessel is increased from \\(300\\text{ K}\\) to \\(320\\text{ K}\\) at constant volume, the measured initial reaction rate increases by a factor of approximately \\(4\\), whereas the calculated total frequency of molecular collisions increases by only about \\(3\\%\\). Which of the following best explains why the reaction rate increases so significantly compared to the collision frequency?"
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url: "https://nerd-notes.com/ubq/119656/"
date_modified: "2026-08-21T08:11:57+00:00"
---

# A student investigates the rate of the gas-phase decomposition of nitrogen dioxide represented by the equation below:

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

When the temperature of the reaction vessel is increased from \(300\text{ K}\) to \(320\text{ K}\) at constant volume, the measured initial reaction rate increases by a factor of approximately \(4\), whereas the calculated total frequency of molecular collisions increases by only about \(3\%\). Which of the following best explains why the reaction rate increases so significantly compared to the collision frequency?

A student investigates the rate of the gas-phase decomposition of nitrogen dioxide represented by the equation below:

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

When the temperature of the reaction vessel is increased from \(300\text{ K}\) to \(320\text{ K}\) at constant volume, the measured initial reaction rate increases by a factor of approximately \(4\), whereas the calculated total frequency of molecular collisions increases by only about \(3\%\). Which of the following best explains why the reaction rate increases so significantly compared to the collision frequency?

- **A.** The reaction rate increases significantly because the fraction of molecular collisions with kinetic energy equal to or greater than the activation energy, \(E_a\), increases substantially.
- **B.** The reaction rate increases significantly because the activation energy, \(E_a\), of the reaction decreases as the temperature is raised.
- **C.** The reaction rate increases significantly because the increase in average molecular speed ensures that all collisions occur with the proper molecular orientation.
- **D.** The reaction rate increases significantly because the total frequency of molecular collisions scales exponentially with absolute temperature.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119656/*