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Half life of a First order reaction is 45 minutes. How long does it need to complete 99.9% of the reaction?

Options

  1. A5 hours
  2. B7.5 hours
  3. C10 hours
  4. D20 hours

Correct answer

B. 7.5 hours

Step-by-step solution

k = 0.693 45 mi n - 1 = 2.303 t 99.9% log a a - 0.999 a or t 99.9% = 2.303 × 45 0.693 log1 0 3 = 448 min ≈ 7.5 h r s

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