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🧪 Chemistry  ·  Chemical Kinetics  ·  NEET & JEE

The half-life of a first-order reaction:

Answer: Is independent of initial concentration.

  • A Depends on initial concentration
  • B Is independent of initial concentration
  • C Doubles with time
  • D Decreases over time

Correct answer: B. Is independent of initial concentration

Explanation: For first-order reactions, t½ = 0.693/k, which is constant and independent of concentration.

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 →