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KCET2025ChemistryChemical Kinetics

Half-life of a first order reaction is 20 seconds and initial concentration of reactant is 0.2 M . The concentration of reactant left after 80 seconds is

Options

  1. A0.1 M
  2. B0.05 M
  3. C0.0125 M
  4. D0.2 M

Correct answer

C. 0.0125 M

Step-by-step solution

no. of Half lives = t t _ 1 2 = 80 20 =4 aligned & [ A _ t ]= [ A _o ] ( 1 2 )^ n & [ A _ t ]=0.2 ( 1 2 )^4=0.0125 aligned

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