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chemistry / Reactions / free

Catalysis

Open a lower-energy pathway and watch a reaction speed up without being consumed.

Follow the cause1 / 3

A catalyst binds or organizes. The catalyst creates an alternative sequence of elementary steps.

activation pathwaypathway · Ea 41 / 86 kJ/mol
Focus the idea
A catalyst lowers activation energy without changing the endpointsThe uncatalyzed barrier is 86 kJ/mol and the catalyzed barrier is 41 kJ/mol. At 45 °C the catalyzed reaction is 3.0e+7 times faster.reactantsproductsk = A e⁻ᴱᵃ⧸ᴿᵀwithout catalystwith catalyst
Ea (kJ/mol)41 vs 86
uncatalyzed k (vs 25 °C)8.85×
catalyzed k (vs 25 °C)2.6e+8×
speed-up3.0e+7×

At 45 °C (318 K) the uncatalyzed rate constant is 8.85× its 25 °C value, and the catalyzed path is 3.0e+7× faster than that. Lowering Ea by 46 kJ/mol multiplies k by e^(ΔEa/RT); heating raises both paths.

Rates use the Arrhenius equation with the same pre-exponential factor for both paths and are relative to the uncatalyzed reaction at 25 °C. A catalyst is not a fuel and is not consumed overall, though it can participate in intermediate steps.

04 / PRACTICE

Make the chemistry yours.

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Answer from the model, then use the explanation to connect the particle picture to the chemical rule.

CHECK 1 / 3

What does a catalyst leave unchanged?