All Flashcards
How do you determine the rate law from a reaction mechanism?
- 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?
- 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?
- 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 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.
What are the key differences between catalysts and intermediates?
Catalysts: Speed up the reaction but are not consumed; not part of the overall reaction. Intermediates: Formed and consumed during the reaction; not present in the overall reaction.
Difference between rate law derived from RDS and overall balanced equation?
Rate Law from RDS: Determined by the reactants in the rate-determining step; must be verified experimentally. Overall Balanced Equation: Represents the stoichiometry of the reaction; does not directly indicate the rate.