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A first-order reaction has a half-life of 69.3 s. At a reactant concentration of 0.10 mol L⁻¹, what is the rate of reaction?

1. 10⁻⁴ M sec⁻¹
2. 10⁻³ M sec⁻¹
3. 10⁻¹ M sec⁻¹
4. 6.93 x 10⁻¹ M sec⁻¹

Correct answer: 10⁻³ M sec⁻¹

Solution

k = 0.693/69.3 = 1 x 10⁻² s⁻¹; rate = k[A] = 1e-2 * 0.10 = 1 x 10⁻³ M s⁻¹.

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