A-LevelChemistryChemical energetics9701/12 · May/June 2011 · Q91 Mark
In the conversion of compound X into compound Z, it was found that the reaction proceeded by way of compound Y, which could be isolated. The following steps were involved. X → Y ; ΔH, positive Y → Z ; ∆H, negative Which reaction profile fits these data? [Figure 9.1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
A[Diagram A: Reaction profile with X as reactant, Y as intermediate (higher energy than X), Z as product (lower energy than Y but higher than X), with activation barriers shown]
B[Diagram B: Reaction profile with X as reactant, Y as intermediate (higher energy than X), Z as product (lower energy than Y but lower than X), with activation barriers shown]
C[Diagram C: Reaction profile with X as reactant, Y as intermediate (lower energy than X), Z as product (lower energy than Y), with activation barriers shown]
D[Diagram D: Reaction profile with X as reactant, Y as intermediate (higher energy than X), Z as product (lower energy than X but higher than Y), with activation barriers shown]
✓ Correct answer
A: [Diagram A: Reaction profile with X as reactant, Y as intermediate (higher energy than X), Z as product (lower energy than Y but higher than X), with activation barriers shown]
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