Answer: twice.
- A equal to
- B twice
- C three times
- D half
Correct answer: B. twice
Explanation: 75% completion leaves 25% (one quarter), which corresponds to two half-lives.
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.