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title: "A chemist investigates the reaction between nitrogen dioxide and carbon monoxide represented by the following balanced equation:  \\[ \\text{NO}_2(g) + \\text{CO}(g) \\rightarrow \\text{NO}(g) + \\text{CO}_2(g) \\]  Two different mechanisms are proposed for the reaction:  Mechanism 1 (single elementary step): \\[ \\text{NO}_2(g) + \\text{CO}(g) \\rightarrow \\text{NO}(g) + \\text{CO}_2(g) \\]  Mechanism 2 (two-step mechanism): \\[ \\text{Step 1 (slow): } 2\\,\\text{NO}_2(g) \\rightarrow \\text{NO}_3(g) + \\text{NO}(g) \\] \\[ \\text{Step 2 (fast): } \\text{NO}_3(g) + \\text{CO}(g) \\rightarrow \\text{NO}_2(g) + \\text{CO}_2(g) \\]  Which of the following experimental results would provide the most decisive evidence to support Mechanism 2 over Mechanism 1?"
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url: "https://nerd-notes.com/ubq/119711/"
date_modified: "2026-08-21T08:12:07+00:00"
---

# A chemist investigates the reaction between nitrogen dioxide and carbon monoxide represented by the following balanced equation:

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

Two different mechanisms are proposed for the reaction:

Mechanism 1 (single elementary step):
\[ \text{NO}_2(g) + \text{CO}(g) \rightarrow \text{NO}(g) + \text{CO}_2(g) \]

Mechanism 2 (two-step mechanism):
\[ \text{Step 1 (slow): } 2\,\text{NO}_2(g) \rightarrow \text{NO}_3(g) + \text{NO}(g) \]
\[ \text{Step 2 (fast): } \text{NO}_3(g) + \text{CO}(g) \rightarrow \text{NO}_2(g) + \text{CO}_2(g) \]

Which of the following experimental results would provide the most decisive evidence to support Mechanism 2 over Mechanism 1?

A chemist investigates the reaction between nitrogen dioxide and carbon monoxide represented by the following balanced equation:

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

Two different mechanisms are proposed for the reaction:

Mechanism 1 (single elementary step):
\[ \text{NO}_2(g) + \text{CO}(g) \rightarrow \text{NO}(g) + \text{CO}_2(g) \]

Mechanism 2 (two-step mechanism):
\[ \text{Step 1 (slow): } 2\,\text{NO}_2(g) \rightarrow \text{NO}_3(g) + \text{NO}(g) \]
\[ \text{Step 2 (fast): } \text{NO}_3(g) + \text{CO}(g) \rightarrow \text{NO}_2(g) + \text{CO}_2(g) \]

Which of the following experimental results would provide the most decisive evidence to support Mechanism 2 over Mechanism 1?

- **A.** Demonstrating that the reaction has a negative standard enthalpy change, \(\Delta H^\circ < 0\), by measuring the temperature rise in an insulated reaction vessel during the conversion.
- **B.** Confirming that the total pressure of the gaseous mixture remains constant over time when the reaction is carried out in a rigid container at constant temperature.
- **C.** Observing that doubling the initial partial pressure of \(\text{CO}(g)\) at constant partial pressure of \(\text{NO}_2(g)\) causes no change in the initial rate of product formation.
- **D.** Showing that increasing the reaction temperature leads to an increase in the measured rate constant and an accelerated overall rate of \(\text{CO}_2(g)\) production.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119711/*