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🧪 Chemistry  ·  Chemical Kinetics  ·  NEET & JEE

For a first-order reaction, a plot of log[A] against time is a straight line whose slope equals:

Answer: -k/2.303.

  • A -k/2.303
  • B -k
  • C +k/2.303
  • D -2.303 k

Correct answer: A. -k/2.303

Explanation: The integrated first-order equation gives log[A] = log[A]<sub>0</sub> - (k/2.303)t, so the slope of log[A] versus t is -k/2.303.

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 →