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In a first-order reaction the reactant concentration falls from 1.0 M to 0.25 M in 20 minutes. What is the rate constant of the reaction?
- 10 min⁻¹
- 6.931 min⁻¹
- 0.6931 min⁻¹
- 0.06931 min⁻¹
Correct answer: 0.06931 min⁻¹
Solution
k = (2.303/20) log(1/0.25) = (2.303/20)(0.602) = (1.386)/20 = 0.0693 min⁻¹.
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