O Levels Chemistry (5070)•5070/12/M/J/19
Explanation
Energy Profile Analysis for Endothermic Reaction
Steps:
- Identify if the reaction is endothermic: products at higher energy than reactants (ΔH > 0).
- Locate activation energies: forward Ea from reactants to peak; backward Ea from products to peak.
- Compare Ea values: for endothermic, forward Ea exceeds backward Ea by ΔH amount.
- Match to options: forward endothermic with greater forward Ea fits D.
Why D is correct:
- In endothermic reactions (ΔH > 0), forward activation energy is larger than backward, as Ea_forward = Ea_backward + ΔH (from reaction energy diagram principles).
Why the others are wrong:
- A: Backward Ea is smaller, not greater, in endothermic reactions.
- B: Backward reaction is exothermic (not endothermic) if forward is endothermic.
- C: Forward is endothermic but backward Ea is smaller, not greater.
Final answer: D
Topic: Exothermic and endothermic reactions
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