EXAM PRACTIVE QUESTIONS Chapter 16 1 The gas phase reaction A B cid 111 C has an experimentally determined rate expression that follows the relationship rate k A 2 What is the reaction order of B Answer zero 2 Which of the following reactions would you predict to occur at the faster rate Answer I nature of the reactants 3 I Ag II CH4 g O2 g cid 111 CO2 g H2O g aq cid 111 AgCl s aq Cl The gas phase reaction A B cid 111 C has an experimentally determined rate expression that follows the relationship rate k A 2 B If the concentration of A is tripled and the concentration of B is doubled the reaction rate would be increased by a factor of Answer 18 4 Determine the reaction rate law expression for the reaction below 2 A B2 C cid 111 A2B BC Trial Initial B2 Initial C Initial Rate of Formation of Initial A 0 20 M 0 40 M 0 20 M 0 20 M 1 2 3 4 0 20 M 0 30 M 0 30 M 0 40 M 0 20 M 0 20 M 0 20 M 0 40 M BC 2 4 cid 117 10 6 M cid 152 min 1 9 6 cid 117 10 6 M cid 152 min 1 2 4 cid 117 10 6 M cid 152 min 1 4 8 cid 117 10 6 M cid 152 min 1 Answer rate k A 2 C 5 Calculate the rate constant k for the reaction described in Question 4 Answer 3 3 cid 117 103 M 2 min 1 6 Consider a chemical reaction involving compounds A and B which is found to be first order in A and second order in B At what rate will the reaction occur in experiment 2 Answer 1 8 M s 1 Experiment Rate M s 1 1 2 0 10 Initial A 1 0 M 2 0 M Initial B 0 20 M 0 60 M 7 The rate constant for the first order reaction A cid 111 B C is k 3 3 cid 117 10 2 min 1 at 57 K What is the half life for this reaction at 57 K Answer 21 min 8 Cyclopropane rearranges to form propene in a reaction that is first order If the rate constant is 2 74 cid 117 10 3 s 1 how long would it take for 85 6 of the cyclopropane to rearrange if the initial concentration was 0 460 M Answer 706 s 9 At a certain temperature the reaction 2B cid 111 C D obeys the rate law expression rate 1 14 cid 117 10 3 M 1 s 1 B 2 If 5 00 mol of B is initially present in a 1 99 L container at that temperature how long would it take for 2 00 mol of B to be consumed at constant temperature Answer 58 3 s 10 Compounds A and B react to form C and D in a reaction that is found to be second order overall and second order in B The rate constant at 50 cid 113 C is 2 48 L mol min What is the half life of B in min if 0 822 M B reacts with excess A Answer 0 491 min 11 The specific rate constant k for a reaction is 2 64 cid 117 10 2 s 1 at cid 113 C and the activation energy is 74 0 kJ mol Calculate k at 50 cid 113 C Answer 0 266 s 1 12 The following mechanism was proposed for a reaction Write the overall reaction and the rate law expression for the proposed mechanism H2 CO cid 111 H2CO slow H2 H2CO cid 111 CH4 O fast H2 O cid 111 H2O fast Answer overall reaction 3 H2 CO cid 111 CH4 H2O rate law expression rate k H2 CO