College Board-Aligned Original Notes
AP Chemistry 5.7: Catalysis
Explain how catalysts increase reaction rate without being consumed.
Aligned to Kinetics from the current College Board AP Chemistry course outline. Exam weighting for this unit: 7%-9% of the multiple-choice score range listed by College Board.
What To Know
- Catalysts provide an alternate pathway with lower activation energy.
- Catalysts do not change the overall enthalpy change.
- Catalysts are regenerated and are not consumed overall.
Detailed Notes
Catalysis is part of Unit 5: Kinetics. The main skill is to explain how catalysts increase reaction rate without being consumed. Before answering, decide whether the prompt is asking for a particulate explanation, a mathematical setup, a graph interpretation, or a connection between more than one representation.
The first idea to keep straight is that catalysts provide an alternate pathway with lower activation energy. In the same topic, remember that catalysts do not change the overall enthalpy change. A complete AP answer also uses the fact that catalysts are regenerated and are not consumed overall. These ideas should be tied to specific particles, charges, attractions, energy changes, or measured quantities rather than stated as isolated facts.
For calculations or symbolic work, anchor the solution with catalyst lowers Ea but does not change delta H. Define what each quantity represents, substitute values with units, and check whether the sign, magnitude, charge balance, atom balance, or equilibrium direction makes chemical sense for this topic.
A catalyst changes the mechanism, not the thermodynamic favorability. In a free-response explanation, state the chemistry concept first, show the relevant equation or representation, and then explain how the evidence supports the conclusion for catalysis.
Key Vocabulary
Catalyst
A substance that speeds a reaction by providing a lower-energy pathway and is regenerated.
Homogeneous catalyst
A catalyst in the same phase as the reactants.
Heterogeneous catalyst
A catalyst in a different phase from the reactants.
Alternate pathway
A different mechanism with lower activation energy.
Useful Relationships
Worked Study Approach
A catalyst changes the mechanism, not the thermodynamic favorability.
Common Mistakes
- Using a memorized rule without explaining the chemical reason behind it.
- Forgetting to conserve atoms, charge, energy, or units when the topic involves calculations.
- Mixing up particle-level explanations with macroscopic observations.
Quick Practice
How would you explain Catalysis in one sentence?
Use the focus statement above, then add one particle-level or mathematical detail.
What evidence would support an AP-style answer on this topic?
Use a balanced equation, diagram, graph, table, numerical setup, or particulate model depending on the prompt.