NJC Physical Chemistry Revision – Kinetics

National Junior College 2016 H2 Chemistry Revision Package Physical Chemistry Revision – Kinetics MCQ 1 [CJC 2011] Two substances, A and B, react according to the following equation: A + 2 B → C To determine the order of reaction with respect to each substance, four experiments were performed and the results are shown below: Experiment [A] / mol dm-3 [B] / mol dm-3 Initial rate of formation of C / mol dm-3 min-1 1 0.10 0.10 0.0010 2 0.40 0.10 0.0160 3 0.10 0.20 0.0020 4 0.20 0.20 ? Which is the correct value for the initial rate of formation of C for experiment 4? A 0.0040 B 0.0080 C 0.0160 D 0.0320 2 [VJC 2009] An experiment was carried out to investigate the initial rate of reaction between ammonium peroxodisulfate, (NH 4)2S2O8, an oxidising agent, and potassium iodide, KI. The initial concentrations of (NH 4)2S2O8 and KI solutions in the mixture together with the time taken for the mixture to darken for the various experimental runs are given below. Initial [(NH4)2S2O8] /mol dm-3 Initial [KI] /mol dm-3 Time taken to darken /s 0.10 0.20 35 0.05 0.20 70 0.10 0.067 105 0.02 0.75 ? What is the expected time taken(in seconds) to darken when the experiment is repeated using initial concentrations of(NH4)2S2O8 and KI to be 0.02 mol dm-3 and 0.75 mol dm-3 respectively?

National Junior College 2016 H2 Chemistry Revision Package A 40 B 47 C 60 D 72 3 [VJC 2009] Which of the following statements best explains why a small increase in temperature leads to a significant increase in the rate of a gaseous reaction? A The frequency of collisions between the molecules is greater at a higher temperature. B The activation energy of the reaction is lower when the gases are at a higher temperature. C The average kinetic energy of the molecules is greater at a higher temperature. D The frequency of effective collisions between molecules with kinetic energy greater than the activation energy is greater at a higher temperature. 4 [HCI 2007] 5 The following data were obtained from the studies of the reaction between NO and O2 in a vessel at constant temperature. Which of the following statements are true regarding the above reaction? 1 The overall order of the reaction is 2. 2 The rate-determining step involves 1 oxygen molecule.

National Junior College 2016 H2 Chemistry Revision Package 3 The rate constant has units of atm−2s−1. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 6 [PJC 2011] The kinetics of the reaction between iodide and peroxodisulfate can be investigated by varying the volume of the reactants used. The two reactants are mixed in the presence of a known and small amount of Na2S2O3 and a little starch. S2O82-(aq) + 2I-(aq) → 2SO42-(aq) + I2(aq) The time taken for an intense blue colour to be observed is then determined. Experiment Volume used / cm3 Time / s 1.0 mol dm-3 KI 0.040 mol dm-3 Na2S2O8 H2O 1 10.0 5.0 25.0 170 2 15.0 5.0 20.0 11