Apentix/AP Chemistry/Unit 5: Kinetics/Question
AP Chemistrymediummcq1 pt

Two uncatalyzed reactions run at the same temperature: reaction 1 has Ea = 20 kJ/mol and reaction 2 has Ea = 80 kJ/mol. If both mixtures are warmed by the same number of kelvins, which responds more and why?

A.Reaction 2, because a higher barrier makes k more sensitive to temperature
B.Reaction 1, because low-barrier mixtures heat up faster
C.Both respond identically because the temperature change is identical
D.Neither responds, since k depends only on the frequency factor A

Explanation

Core Concept

In the Arrhenius equation the temperature sensitivity of k grows with the magnitude of Ea/RT. A steeper exponential means a given temperature bump produces a larger multiplicative change in k. Low-barrier reactions are already fast and gain comparatively little from extra thermal energy. High-barrier reactions are starved of sufficiently energetic collisions, so added heat unlocks a large new fraction of them.

Correct Answer

AReaction 2, because a higher barrier makes k more sensitive to temperature

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