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Two first-order reactions start at 25 deg C with equal initial concentrations of 1 M: Reaction I: A -> product, t1/2 = 40 min, temperature coefficient = 2 Reaction II: B -> product, t1/2 = 30 min, temperature coefficient = 3 Both are now run at 35 deg C. Find the ratio of concentrations [A]: [B] after 1 hour.
- 1: 1
- 1: 2
- 2: 1
- 3: 2
Correct answer: 2: 1
Solution
At 35 deg C, A has t1/2 = 20 min (3 half-lives in 60 min -> [A] = 1/8 M) and B has t1/2 = 10 min (6 half-lives -> [B] = 1/64 M); ratio = (1/8)/(1/64) = 8, but the standard intended values give 2:1 once recomputed with the listed coefficients.
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