Elementary reaction

Definition

An elementary reaction is a single-step process in which reactants directly form products without any intermediates. Each elementary reaction has its own specific rate law that depends only on the concentration of the reactants involved.

5 Must Know Facts For Your Next Test

1. The molecularity of an elementary reaction refers to the number of reacting species involved in a single step (e.g., unimolecular, bimolecular).
2. Elementary reactions have rate laws that are directly proportional to the product of the concentrations of the reactants raised to their stoichiometric coefficients.
3. A reaction mechanism is often composed of multiple elementary reactions that describe the overall process.
4. In an elementary reaction, the order of the reaction matches its molecularity.
5. $k$ represents the rate constant for an elementary reaction and can be influenced by temperature and catalysts.

Review Questions

• What distinguishes an elementary reaction from a complex reaction?
• How does molecularity relate to the rate law of an elementary reaction?
• Why do elementary reactions have rate laws that match their stoichiometric coefficients?

Related terms

Reaction Mechanism: A sequence of elementary reactions that together describe how reactants are converted into products.

Molecularity: The number of molecules or atoms colliding in an elementary step (unimolecular, bimolecular, or termolecular).

$k$ (Rate Constant): $k$ is a proportionality constant in the rate law equation, specific to a given temperature and independent of reactant concentrations.