Ch 12 - AP Chemistry

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Ch 12 - AP Chemistry

Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsPRACTICE PROBLEMSReaction RatesSuggested Problems on p 567: 19, 21, 23, 25, 29, 31, 35, 39, 43, 47, 49, 51, 53, 55, 57, 63, 65, 6920. In the Haber process for the production of ammonia,N 2 (g) + 3H 2 (g) 2NH 3 (g)what is the relationship between the rate of production of ammonia and the rate ofconsumption of hydrogen?22. Consider the general reactionaA + bB cCand the following average rate data over some time period ∆t:Determine a set of possible coefficients to balance this general reaction.Page 1 of 62014 mrluzio.com/apchem12


Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsRate Laws from Experimental DataPRACTICE PROBLEMS26. The reaction2 I - (aq) + S 2 O 2- 8 (aq) I 2 (aq) + 2 SO 2- 4 (aq)was studied at 25°C. The following results were obtained where[ ][I - ] 0 (mol/L) [S 2 O 2- 8 ] 0 (mol/L) Initial Rate (mol/L•s)0.080 0.040 12.5 x 10 -60.040 0.040 6.25 x 10 -60.080 0.020 6.25 x 10 -60.032 0.040 5.00 x 10 -60.060 0.030 7.00 x 10 -6a. Determine the rate law.b. Calculate a value for the rate constant for each experiment and an average value for therate constant.34. A certain reaction has the following general form:aA bBAt a particular temperature and [A] 0 = 2.80 x 10 -3 M, concentration versus time data werecollected for this reaction, and a plot of 1/[A] versus time resulted in a straight line with a slopevalue of +3.60 x 10 -2 L/mol•s.a. Determine the rate law, the integrated rate law, and the value of the rate constant forthis reaction.b. Calculate the half-life for this reaction.c. How much time is required for the concentration of A to decrease to 7.00 x 10 -4 M?Page 2 of 62014 mrluzio.com/apchem12


Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsReaction MechanismsPRACTICE PROBLEMS50. For the reaction2 H 2 (g) + 2 NO(g) N 2 (g) + 2 H 2 O(g)the observed rate law isRate = k[NO] 2 [H 2 ]Which of the following are acceptable mechanisms for this reaction? Explain.Mechanism I:2 H 2 (g) + 2 NO(g) N 2 (g) + 2 H 2 O(g)Mechanism II:H 2 (g) + NO(g) H 2 O(g) + N(g)N(g) + NO(g) N 2 (g) + O(g)H 2 (g) + O(g) H 2 O(g)Mechanism III:H 2 (g) + 2 NO(g) N 2 O(g) + H 2 O(g)N 2 O(g) + H 2 (g) N 2 (g) + H 2 O(g)SlowFastFastSlowFast52. The mechanism for the reaction of nitrogen dioxide with carbon monoxide to form nitricoxide and carbon dioxide is thought to beNO 2 + NO 2 NO 3 + NOSlowNO 3 + CO NO 2 + CO 2FastWrite the rate law expected for this mechanism. What is the overall balanced equation for thereaction?Page 3 of 62014 mrluzio.com/apchem12


Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsPRACTICE PROBLEMS1. An environmental concern is the depletion of O 3 in Earth’s upper atmosphere, where O 3 isnormally in equilibrium with O 2 and O. A proposed mechanism for the depletion of O 3 inthe upper atmosphere is shown below.Step 1: O 3 + Cl O 2 + ClO fastStep 2: ClO + O Cl + O 2 slow(a) Write a balanced chemical equation for the overall reaction represented by Step 1 andStep 2 above.(b) Clearly identify the catalyst in the mechanism above. Justify your answer.(c) Clearly identify the intermediate in the mechanism above. Justify your answer.(d) Determine each of the following.(i) the rate law for the overall reaction(ii) the appropriate units for the rate constant, k(e) In general, what effect, if any, does the addition of a catalyst have on each of thefollowing in a chemical reaction? Sketching and labeling potential energy diagramscould be very helpful in answering this question.(i) the potential energy of the reactants(ii) the potential energy of the activated complex(iii) the potential energy of the productsPage 4 of 62014 mrluzio.com/apchem12


Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsTemperature Dependence of Rate ConstantsPRACTICE PROBLEMS58. The reaction(CH 3 ) 3 CBr + OH - (CH 3 ) 3 COH + Br -in a certain solvent is first order with respect to (CH 3 ) 3 CBr and zero order with respect to OH - .In several experiments, the rate constant k was determined at different temperatures. A plotof ln(k) versus 1/T was constructed resulting in a straight line with a slope value of -1.10 x 10 4 Kand y-intercept of 33.5. Assume k has units of s -1 .a. Determine the activation energy for this reaction.b. Determine the value of the frequency factor A.c. Calculate the value of k at 25°C.Page 5 of 62014 mrluzio.com/apchem12


Name:_______________________________ Date:_________________ Hr:____AP CHEMISTRYCh 12Chemical KineticsCatalysisPRACTICE PROBLEMS68. The decomposition of NH 3 to N 2 and H 2 was studied on twosurfaces. Without a catalyst, the activation energy is 335 kJ/mol.a) Which surface is the better heterogeneous catalyst for thedecomposition of NH 3 ? Why?Surface E a (kJ/mol)W 163Os 197b) How many times faster is the reaction at 298 K on the W surface compared with thereaction with no catalyst present? Assume that the frequency factor A is the same foreach reaction.c) The decomposition reaction on the two surfaces obeys a rate law of the formHow can you explain the inverse dependence of the rate on the H 2 concentration?Page 6 of 62014 mrluzio.com/apchem12

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