Q. The bromination of acetone that occurs in acid solution is represented by this equation CH₃COCH₃(aq) + Br₂(aq) → CH₃COCH₂Br(aq) + H⁺(aq) + Br⁻(aq) These kinetic data were obtained for given reaction concentrations. Initial concentrations (M) [CH₃COCH₃], [Br₂], [H⁺] → initial rate of disappearance of Br₂ (M s⁻¹): 0.30, 0.05, 0.05 → 5.7 × 10⁻⁵ 0.30, 0.10, 0.05 → 5.7 × 10⁻⁵ 0.30, 0.10, 0.10 → 1.2 × 10⁻⁴ 0.40, 0.05, 0.20 → 3.1 × 10⁻⁴ Based on these data, the rate equation is
A) Rate = k[CH₃COCH₃][Br₂][H⁺]
B) Rate = k[CH₃COCH₃][H⁺]
C) Rate = k[CH₃COCH₃][Br₂]
D) Rate = k[CH₃COCH₃][Br₂][H⁺]²
Explanation
[Solution from source] Runs 1 and 2: doubling [Br₂] leaves the rate unchanged, so the reaction is zero order in Br₂. Runs 2 and 3: doubling [H⁺] doubles the rate, so it is first order in H⁺. Run 4 checks acetone: 5.7 × 10⁻⁵ × (0.40/0.30) × (0.20/0.05) ≈ 3.0 × 10⁻⁴, matching 3.1 × 10⁻⁴, so it is first order in acetone. Rate = k[CH₃COCH₃][H⁺]; any form containing [Br₂] contradicts runs 1 and 2. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.