All Flashcards
What is a reaction mechanism?
The step-by-step sequence of elementary reactions by which overall chemical change occurs.
Define an elementary step.
An individual, simple reaction that represents a single molecular event in a reaction mechanism.
What is a catalyst?
A substance that speeds up a reaction without being consumed in the process; it lowers the activation energy.
Define an intermediate.
A species formed during a reaction and then consumed in a subsequent step; it is not a reactant or product.
What is the rate-determining step?
The slowest step in a reaction mechanism; it controls the overall rate of the reaction.
What is activation energy?
The minimum energy required for a chemical reaction to occur.
What is the effect of a catalyst on the activation energy?
A catalyst lowers the activation energy of a reaction.
What happens if the rate-determining step includes an intermediate?
You'll need to use equilibrium concepts to substitute the intermediate out of the rate law.
What happens if you increase the concentration of a reactant in the rate-determining step?
The overall rate of the reaction will increase.
How do you determine the overall reaction from a mechanism?
Add all the elementary steps together and cancel out any species that appear on both sides of the equation (intermediates and catalysts).
How to determine the rate law from a reaction mechanism?
Identify the rate-determining step. The rate law for the overall reaction is the same as the rate law for the rate-determining step, based on its stoichiometry.
What is the first step to solve a mechanism problem?
Identify the rate-determining step.