Question Detail
Question
The isomerization of cyclopropane to form propene is a first-order reaction. At 760 K, 15% of a sample of cyclopropane changes to propene in 6.8 min. What is the half-life of cyclopropane at 760 K?
Correct Answer
Option A is the correct answer.
Detailed Explanation
First-order: ln([A]₀/[A]) = kt. 15% reacted means 85% remains: [A]/[A]₀ = 0.85. k = (1/6.8) ln(1/0.85) = (1/6.8) × 0.1625 = 0.0239 min⁻¹. t₁/₂ = ln2/k = 0.693/0.0239 = 29.0 min.
Hint
Use first-order integrated rate law to find k, then t₁/₂ = ln2/k.