The mechanism for the gas-phase reaction of nitrogen dioxide...

The mechanism for the gas-phase reaction of nitrogen dioxide with carbon monoxide to form nitric oxide and carbon dioxide is thought to be $$ \begin{array}{c}{\mathrm{NO}_{2}+\mathrm{NO}_{2} \longrightarrow \mathrm{NO}_{3}+\mathrm{NO}} \\ {\mathrm{NO}_{3}+\mathrm{CO} \longrightarrow \mathrm{NO}_{2}+\mathrm{CO}_{2}}\end{array} $$ Write the rate law expected for this mechanism. What is the overall balanced equation for the reaction?

The mechanism for the gas-phase reaction of nitrogen dioxide with carbon monoxide to form nitric oxide and carbon dioxide is thought to be
$$
\begin{array}{c}{\mathrm{NO}_{2}+\mathrm{NO}_{2} \longrightarrow \mathrm{NO}_{3}+\mathrm{NO}} \\ {\mathrm{NO}_{3}+\mathrm{CO} \longrightarrow \mathrm{NO}_{2}+\mathrm{CO}_{2}}\end{array}
$$
Write the rate law expected for this mechanism. What is the overall balanced equation for the reaction?

Key Concepts

Rate-Determining Step

The rate-determining step is the slowest step in a reaction mechanism, and it effectively controls the overall reaction rate. Since the rate law is derived from this step, its molecularity (e.g., unimolecular, bimolecular) directly influences the form of the rate law for the entire process.

Rate Laws

A rate law relates the speed of a reaction to the concentrations of its reactants. In the context of a mechanism, the overall rate law is normally determined by the rate-determining step, meaning that the reaction kinetics can often be modeled by focusing on this key step. This principle allows chemists to predict how changes in concentrations impact the reaction rate.

Overall Reaction Equation

The overall reaction equation represents the net change from reactants to products by summing all elementary steps and canceling out any intermediates. This balanced equation provides a clear view of the stoichiometric relationships involved without the details of the intermediate species formed and consumed during the reaction process.

Reaction Mechanisms

A reaction mechanism is a detailed sequence of elementary steps that describes how reactants are converted into products at the molecular level. It helps in understanding the specific steps, interactions, and intermediates involved, providing a framework to connect the observed kinetics of the overall reaction to the particular molecular events taking place.

Elementary Steps

Elementary steps are the individual reactions that occur in a mechanism. Each of these steps is characterized by a simple, often unimolecular or bimolecular, process whose rate law directly reflects the molecularity of that step. Understanding these steps is crucial because the properties of the rate law for the overall process depend on the slowest of these steps.

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