All Flashcards
What is a reaction mechanism?
A series of elementary steps showing how a reaction occurs at the molecular level.
Define an elementary step.
A single molecular event (e.g., collision, bond breaking/forming).
What are intermediates?
Species produced in one step and consumed in a later step; they don't appear in the overall reaction.
What are catalysts?
Species that speed up a reaction but are not consumed in the overall reaction; they appear in reactants and products.
Define the rate-determining step.
The slowest step in a reaction mechanism; it determines the overall reaction rate.
What is the steady-state approximation?
The assumption that the concentration of intermediates remains constant because their rate of formation equals their rate of consumption.
What is the effect of the rate-determining step on the overall reaction rate?
The rate-determining step limits the overall reaction rate.
What is the effect of a fast and reversible first step on determining the rate law?
The slow step's rate law will often include intermediates, requiring the use of the steady-state approximation to express the rate law in terms of reactants.
What are the steps to apply the steady-state approximation when the first step is fast and reversible?
- Identify the intermediate. 2. Set up equilibrium for the fast, reversible step. 3. Solve for the intermediate's concentration. 4. Substitute the intermediate's expression into the slow step's rate law.