Rate equations, orders and rate constantsAQA A-Level Chemistry: Mind map

Exam questions on Rate equations, orders and rate constants

1. A student investigates the reaction between substances A and B at constant temperature. The reaction has the rate equation rate = k[A][B]², where square brackets show concentrations in mol dm⁻³.
   State what is meant by the statement that the reaction is first order with respect to A.2 marks
2. The initial rate of the reaction between substances P and Q was measured at constant temperature in three experiments. Experiment 1: [P] = 0.10 mol dm⁻³, [Q] = 0.10 mol dm⁻³, initial rate = 2.0 × 10⁻⁴ mol dm⁻³ s⁻¹. Experiment 2: [P] = 0.20 mol dm⁻³, [Q] = 0.10 mol dm⁻³, initial rate = 8.0 × 10⁻⁴ mol dm⁻³ s⁻¹. Experiment 3: [P] = 0.20 mol dm⁻³, [Q] = 0.20 mol dm⁻³, initial rate = 1.6 × 10⁻³ mol dm⁻³ s⁻¹.
   Define the term rate constant, k, and state one factor that changes its value.2 marks
3. In acid solution, propanone reacts with iodine: CH₃COCH₃ + I₂ → CH₃COCH₂I + HI. The initial rate was measured in four experiments, with the concentrations of propanone, H⁺ and I₂ in mol dm⁻³. Experiment 1: 1.00, 0.50, 0.0050, rate = 1.35 × 10⁻⁵ mol dm⁻³ s⁻¹. Experiment 2: 2.00, 0.50, 0.0050, rate = 2.70 × 10⁻⁵. Experiment 3: 1.00, 1.00, 0.0050, rate = 2.70 × 10⁻⁵. Experiment 4: 1.00, 0.50, 0.0100, rate = 1.35 × 10⁻⁵.
   Deduce the order of reaction with respect to each of propanone, H⁺ and I₂. Give your reasoning.3 marks