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A certain zero-order reaction goes to completion in 5 minutes at 200 K and in 2.5 minutes at 300 K. Taking R = 2 cal/(mol*K) and ln 2 = 0.7, what is the activation energy of the reaction (in calories per mole)?
- 840 cal/mol
- 420 cal/mol
- 1680 cal/mol
- 210 cal/mol
Correct answer: 840 cal/mol
Solution
Since k ∝ 1/t, k2/k1 = 5/2.5 = 2, so ln(k2/k1) = 0.7; substituting into the Arrhenius equation with (1/200 - 1/300) gives Ea = 840 cal/mol.
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