Question Detail
Question
It takes 25.0 min for the concentration of a reactant in a first-order reaction to drop from 0.80 M to 0.40 M at 25 °C. What is the rate constant?
Correct Answer
Option A is the correct answer.
Detailed Explanation
For a first-order reaction, k = (1/t) ln([A]₀/[A]) = (1/25) ln(0.80/0.40) = (1/25) ln(2) = (1/25) × 0.693 = 0.02772 min⁻¹ ≈ 0.0277 min⁻¹.
Hint
Use the integrated rate law: ln([A]₀/[A]) = kt.