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MHT CET202613 April 2026Evening ShiftChemistryChemical KineticsActual

The half-life of a first-order reaction is 20 minutes. What is the rate constant (in min ⁻¹ ) for this reaction?

Options

  1. A0.0347
  2. B0.5
  3. C13.86
  4. D34.67

Correct answer

A. 0.0347

Step-by-step solution

For a first-order reaction, the rate constant k is related to the half-life t_ 1/2 by the equation: k = 0.693 t_ 1/2 Given t_ 1/2 = 20 minutes. Substituting the value: k = 0.693 20 k = 0.03465 min ⁻¹ Rounding off, we get k 0.0347 min ⁻¹ . Answer: 0.0347

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