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In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in 15 m i n u t e s . The time taken for the concentration to change from 0.1 M to 0.025 M is -

Options

  1. A30 m i n u t e s
  2. B15 m i n u t e s
  3. C7.5 m i n u t e s
  4. D60 m i n u t e s

Correct answer

A. 30 m i n u t e s

Step-by-step solution

0.1 M → t 1 / 2 0.05 M → t 1 / 2 0.025 M for the I st order reaction :- t 3 / 4 = 2 × t 1 / 2 = 2 × 15 = 30 minute successive half lives in first order reactions remain constant irrespective of initial concentration.

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