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JEE Main levelSingle correct optionDifficulty 2 of 3ck038

A first order reaction has a half-life of . The percentage of the reactant left after is closest to

  1. A
  2. B
  3. C
  4. D

Answer: D

half-lives, so the fraction left is , i.e. . Linear interpolation between 25% and 12.5% (giving 18.75%) is wrong because decay is exponential.
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