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Catalysis

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A catalyst speeds a reaction by providing an alternate pathway with a lower activation energy. It is not consumed (regenerated by the end), it lowers Eₐ for both the forward and reverse directions, and it does not change the reactant or product energies — so ΔH and the equilibrium position are unchanged.

UNIT 5 TOPIC 5.11 • CATALYSIS CATALYSIS potential energy reaction coordinate uncatalyzed pathway catalyzed pathway same reactants same products lower barrier = smaller Eₐ Catalyst facts A catalyst speeds up a reaction by giving an alternate pathway with a lower Eₐ. It does NOT change ΔH, K, or the final equilibrium amounts — only the rate. Catalyst cycle Step 1: A + Cat → A–Cat catalyst is consumed Step 2: A–Cat + B → P + Cat catalyst is regenerated → not used up overall Common modes Binding / orientation of reactants Acid–base catalysis Surface (heterogeneous) catalysis CED ANCHOR 5.11 — catalysts lower Eₐ A catalyst affects the kinetics (rate), not the thermodynamics: ΔH, K, and equilibrium are unchanged. AP Chemistry · Unit 5 · Kinetics
A catalyst provides an alternate pathway with a lower activation energy, speeding the reaction. It is not consumed, it lowers Eₐ for both the forward and reverse directions equally, and it leaves the reactant and product energies (and therefore ΔH and the equilibrium position) unchanged.
Catalyst Lab · Open the sandbox →

The core misconception is misunderstanding what a catalyst does: it lowers the activation barrier, not ΔH, and it does not shift the equilibrium or get used up. A catalyst changes the path and the speed, never the reaction's energetics or endpoint.

The work

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Lesson
Catalysis ›

A catalyst lowers Eₐ via an alternate pathway without being consumed or changing ΔH or equilibrium. The lesson reasons from the energy profile, then closes with a ten-scenario check.

Skill check · 10 scenarios
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Diagnostic
10-item topic check ›

Ten items spanning the Topic 5.11 misconceptions: what a catalyst does misunderstood (lowering Eₐ vs ΔH), and its effect on temperature, collisions, and equilibrium misread.

Not started · 10 items · ~15 min
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Targeted Practice
Drill a single misconception ›

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions
Diagnostic first