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For a first-order reaction with rate constant k = 1.155 x 10⁻³ s⁻¹, after how many seconds will the reactant concentration fall to half its initial value?

1. 600
2. 100
3. 60
4. 10

Correct answer: 600

Solution

t(1/2) = 0.693 / (1.155 x 10⁻³) = 600 s.

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