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Which statement is correct for a first order reaction?

1. Time for completion is finite
2. t1/2 is proportional to 1/a (a = initial concentration)
3. The unit of k is mol L⁻¹ s⁻¹
4. t1/2 * k = constant

Correct answer: t1/2 * k = constant

Solution

For first order, t1/2 = 0.693/k, so t1/2 * k = 0.693 (a constant); half-life is independent of initial concentration, k has units of s⁻¹, and completion time is infinite.

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