How do you determine the rate law from a reaction mechanism?
1. Identify the rate-determining step (slowest step). 2. Write the rate law based on the reactants in the rate-determining step. 3. If the rate law contains an intermediate, substitute using the equilibrium expression of a fast, reversible step.
Steps to verify a proposed reaction mechanism?
1. Derive the rate law from the proposed mechanism's rate-determining step. 2. Compare the derived rate law with the experimentally determined rate law. 3. If they match, the mechanism is consistent with experimental data.
How to find the overall reaction from elementary steps?
1. Write down all the elementary steps in the mechanism. 2. Add all the steps together. 3. Cancel out any species that appear on both the reactant and product sides (intermediates and catalysts). 4. The remaining species form the overall balanced equation.
What is a reaction mechanism?
A detailed, step-by-step sequence of elementary reactions that collectively describe how a chemical reaction occurs.
What is an elementary step?
A single step in a reaction mechanism that represents one molecular event.
What is a catalyst?
A substance that speeds up a reaction without being consumed in the process.
What is an intermediate?
A species that is formed and consumed during the reaction but does not appear in the overall balanced equation.
What is the rate-determining step (RDS)?
The slowest step in a reaction mechanism that determines the overall rate of the reaction.
Define rate law.
An equation that expresses the rate of a reaction in terms of the concentrations of reactants.
What is the effect of the rate-determining step on the overall reaction rate?
The rate-determining step limits the overall reaction rate; the reaction cannot proceed faster than its slowest step.
What is the effect of a catalyst on the activation energy of a reaction?
A catalyst lowers the activation energy of a reaction, thereby increasing the reaction rate.
What happens if the derived rate law from a mechanism does not match the experimental rate law?
The proposed mechanism is not valid and must be revised or discarded.
