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Reaction Energy Profile

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A reaction energy profile plots potential energy along the reaction coordinate. Reactants climb an activation-energy (Eₐ) barrier to a peak — the transition state — then descend to products. The reactant-to-product energy difference is the enthalpy change, ΔH. Eₐ (the barrier height) and ΔH (the net change) are distinct.

UNIT 5 TOPIC 5.6 • REACTION ENERGY PROFILE ENERGY PROFILE Ea,forward Ea,reverse ΔH < 0 transition state reactants products potential energy reaction coordinate Activation Energy (Ea) Ea is the energy difference between the reactants and the transition state. It is the minimum energy needed for the reaction to occur. Thermodynamics vs. Kinetics ΔH compares products to reactants. Ea controls how fast the reaction can occur. Temperature Link Higher temperature means more particles have enough energy to clear the barrier. AP Chemistry · Unit 5 · Kinetics
A reaction energy profile plots potential energy along the reaction coordinate. The peak is the transition state; the climb from reactants to that peak is the activation energy (Eₐ); the net drop (or rise) from reactants to products is ΔH. Eₐ and ΔH are different features — do not confuse them.
Profile Sculptor · Open the sandbox →

The central error is confusing Eₐ with ΔH: Eₐ is the barrier from reactants up to the transition state, while ΔH is the difference between reactants and products. A profile also shows whether a reaction is exothermic (products lower) or endothermic (products higher).

The work

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Lesson
Energy Profiles ›

An energy profile shows the activation barrier (Eₐ) and the enthalpy change (ΔH) as different features. The lesson reads each off the curve without confusing them, 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 5.6 misconceptions: Eₐ and ΔH confused on an energy profile, and the transition state and profile features 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