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Half life period of a first-order reaction is 1386 seconds. The specific rate constant of the reaction is:

1. 0.5 × 10⁻² s⁻¹
2. 0.5 × 10⁻³ s⁻¹
3. 5.0 × 10⁻² s⁻¹
4. 5.0 × 10⁻³ s⁻¹

Correct answer: 0.5 × 10⁻³ s⁻¹

Solution

For a first-order reaction, the half-life (t₁/₂) is related to the rate constant (k) by the formula t₁/₂ = 0.693/k. Substituting t₁/₂ = 1386 s, we get k = 0.693/1386 = 0.5 × 10⁻³ s⁻¹.

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