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🧪 Chemistry  ·  Chemical Kinetics  ·  NEET & JEE

A first-order reaction has a rate constant k = 0.0693 min⁻¹. Its half-life is:

Answer: 10 min.

  • A 5 min
  • B 10 min
  • C 20 min
  • D 100 min

Correct answer: B. 10 min

Explanation: t½ = 0.693/k = 0.693/0.0693 = 10 minutes.

First-Order Decay: Constant Half-Lifetime[A][A]₀[A]₀/22 × t½[A]₀/4Each successive half-life takes the SAME amount of time, regardless of starting concentration

First-order decay curve: concentration halves every t½, and that half-life is constant - a defining test for first-order kinetics.

Concept context

Study the speed of reactions and what affects it: concentration, temperature, and catalysts. Covers rate law, order of reaction, the Arrhenius equation, and reaction mechanisms step by step.

Read the full Chemical Kinetics notes →