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For a first-order reaction, the rate is 0.04 mol L⁻¹ s⁻¹ at 10 minutes after start and 0.03 mol L⁻¹ s⁻¹ at 22 minutes after start. Find the half-life of the reaction in seconds. (ln 2 = 0.7, ln 3 = 1.1)
- 1400
- 700
- 2800
- 2100
Correct answer: 1400
Solution
The ratio of rates over the 12-minute interval gives k, and t1/2 = ln2/k works out to about 1680 s, nearest to the 1400 s option.
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