---
title: "The gas-phase reaction between nitric oxide and chlorine is represented by the balanced equation \\[ 2\\,\\text{NO}(g) + \\text{Cl}_2(g) \\rightarrow 2\\,\\text{NOCl}(g) \\] A proposed mechanism for the reaction consists of two elementary steps:  Step 1 (fast equilibrium): \\(\\text{NO}(g) + \\text{Cl}_2(g) \\underset{k_{-1}}{\\overset{k_1}{\\rightleftharpoons}} \\text{NOCl}_2(g)\\) \\quad (\\(k_1 = 2.0 \\times 10^4 \\text{ M}^{-1}\\cdot\\text{s}^{-1}\\), \\(k_{-1} = 5.0 \\times 10^2 \\text{ s}^{-1}\\))  Step 2 (slow): \\(\\text{NOCl}_2(g) + \\text{NO}(g) \\xrightarrow{k_2} 2\\,\\text{NOCl}(g)\\) \\quad (\\(k_2 = 5.0 \\times 10^1 \\text{ M}^{-1}\\cdot\\text{s}^{-1}\\))  A reaction vessel at the same temperature is initially filled such that \\([\\text{NO}] = 0.020 \\text{ M}\\) and \\([\\text{Cl}_2] = 0.050 \\text{ M}\\). Based on the proposed mechanism, what is the initial rate of the reaction?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/121501/"
date_modified: "2026-08-23T05:04:51+00:00"
---

# The gas-phase reaction between nitric oxide and chlorine is represented by the balanced equation
\[ 2\,\text{NO}(g) + \text{Cl}_2(g) \rightarrow 2\,\text{NOCl}(g) \]
A proposed mechanism for the reaction consists of two elementary steps:

Step 1 (fast equilibrium): \(\text{NO}(g) + \text{Cl}_2(g) \underset{k_{-1}}{\overset{k_1}{\rightleftharpoons}} \text{NOCl}_2(g)\) \quad (\(k_1 = 2.0 \times 10^4 \text{ M}^{-1}\cdot\text{s}^{-1}\), \(k_{-1} = 5.0 \times 10^2 \text{ s}^{-1}\))

Step 2 (slow): \(\text{NOCl}_2(g) + \text{NO}(g) \xrightarrow{k_2} 2\,\text{NOCl}(g)\) \quad (\(k_2 = 5.0 \times 10^1 \text{ M}^{-1}\cdot\text{s}^{-1}\))

A reaction vessel at the same temperature is initially filled such that \([\text{NO}] = 0.020 \text{ M}\) and \([\text{Cl}_2] = 0.050 \text{ M}\). Based on the proposed mechanism, what is the initial rate of the reaction?

The gas-phase reaction between nitric oxide and chlorine is represented by the balanced equation
\[ 2\,\text{NO}(g) + \text{Cl}_2(g) \rightarrow 2\,\text{NOCl}(g) \]
A proposed mechanism for the reaction consists of two elementary steps:

Step 1 (fast equilibrium): \(\text{NO}(g) + \text{Cl}_2(g) \underset{k_{-1}}{\overset{k_1}{\rightleftharpoons}} \text{NOCl}_2(g)\) \quad (\(k_1 = 2.0 \times 10^4 \text{ M}^{-1}\cdot\text{s}^{-1}\), \(k_{-1} = 5.0 \times 10^2 \text{ s}^{-1}\))

Step 2 (slow): \(\text{NOCl}_2(g) + \text{NO}(g) \xrightarrow{k_2} 2\,\text{NOCl}(g)\) \quad (\(k_2 = 5.0 \times 10^1 \text{ M}^{-1}\cdot\text{s}^{-1}\))

A reaction vessel at the same temperature is initially filled such that \([\text{NO}] = 0.020 \text{ M}\) and \([\text{Cl}_2] = 0.050 \text{ M}\). Based on the proposed mechanism, what is the initial rate of the reaction?

- **A.** \(2.5 \times 10^{-5} \text{ M}\cdot\text{s}^{-1}\)
- **B.** \(1.0 \times 10^{-3} \text{ M}\cdot\text{s}^{-1}\)
- **C.** \(2.0 \times 10^{-2} \text{ M}\cdot\text{s}^{-1}\)
- **D.** \(4.0 \times 10^{-2} \text{ M}\cdot\text{s}^{-1}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121501/*