---
title: "A student investigates the gas-phase formation of nitrosyl bromide, represented by the overall reaction  \\[2\\text{NO(g)}+\\text{Br}_2\\text{(g)}\\rightarrow 2\\text{NOBr(g)}\\]  The following two-step mechanism is proposed.  \\[\\text{NO(g)}+\\text{Br}_2\\text{(g)}\\rightleftharpoons\\text{NOBr}_2\\text{(g)}\\qquad \\text{fast}\\;(k_1,k_{-1})\\]  \\[\\text{NOBr}_2\\text{(g)}+\\text{NO(g)}\\rightarrow 2\\text{NOBr(g)}\\qquad \\text{slow}\\;(k_2)\\]  Which of the following is the rate law for the overall reaction expressed only in terms of reactant concentrations and elementary-step rate constants?"
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url: "https://nerd-notes.com/ubq/119319/"
date_modified: "2026-08-19T12:39:47+00:00"
---

# A student investigates the gas-phase formation of nitrosyl bromide, represented by the overall reaction

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

The following two-step mechanism is proposed.

\[\text{NO(g)}+\text{Br}_2\text{(g)}\rightleftharpoons\text{NOBr}_2\text{(g)}\qquad \text{fast}\;(k_1,k_{-1})\]

\[\text{NOBr}_2\text{(g)}+\text{NO(g)}\rightarrow 2\text{NOBr(g)}\qquad \text{slow}\;(k_2)\]

Which of the following is the rate law for the overall reaction expressed only in terms of reactant concentrations and elementary-step rate constants?

A student investigates the gas-phase formation of nitrosyl bromide, represented by the overall reaction

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

The following two-step mechanism is proposed.

\[\text{NO(g)}+\text{Br}_2\text{(g)}\rightleftharpoons\text{NOBr}_2\text{(g)}\qquad \text{fast}\;(k_1,k_{-1})\]

\[\text{NOBr}_2\text{(g)}+\text{NO(g)}\rightarrow 2\text{NOBr(g)}\qquad \text{slow}\;(k_2)\]

Which of the following is the rate law for the overall reaction expressed only in terms of reactant concentrations and elementary-step rate constants?

- **A.** \(\text{rate}=k_2[\text{NOBr}_2][\text{NO}]\)
- **B.** \(\text{rate}=\dfrac{k_1k_2}{k_{-1}}[\text{NO}][\text{Br}_2]\)
- **C.** \(\text{rate}=\dfrac{k_{-1}k_2}{k_1}[\text{NO}]^2[\text{Br}_2]\)
- **D.** \(\text{rate}=\dfrac{k_1k_2}{k_{-1}}[\text{NO}]^2[\text{Br}_2]\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119319/*