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ChemistryNEET 2025Integrated rate equations and half-life

Chemical Kinetics

If the half-life (t1/2t_{1/2}) for a first-order reaction is 1 minute, then the time required for 99.9% completion of the reaction is closest to:

  1. A.2 minutes
  2. B.4 minutes
  3. C.5 minutes
  4. D.10 minutes✓

Solution

99.9% completion leaves 11000\frac{1}{1000} of the reactant, i.e. about 2102^{10}-fold reduction — ten half-lives. t≈10×1=10t \approx 10 \times 1 = 10 minutes.

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