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A second-order reaction has a rate constant of 8 * 10⁻⁵ M⁻¹ min⁻¹. How long will it take for a 1 M solution to fall to 0.5 M?

1. 8.665 * 10³ min
2. 8 * 10⁻³ min
3. 1.25 * 10⁴ min
4. 4 * 10⁻⁵ min

Correct answer: 1.25 * 10⁴ min

Solution

Second-order half-life t = 1/(k[A]0) = 1/(8*10⁻⁵ * 1) = 1.25*10⁴ min.

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