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Name: __________________________ Date: _____________ 1. Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO2(aq) + 2OH–(aq) ClO2–(aq) + ClO3–(aq) + H2O(l) Under a certain set of conditions, the initial rate of disappearance of chlorine dioxide was determined to be 2.30 x 10–1 M/s. What is the initial rate of appearance of chlorite ion under those same conditions? A) 5.75 x 10–2 M/s B) 1.15 x 10–1 M/s C) 2.30 x 10–1 M/s D) 4.60 x 10–1 M/s E) 9.20 x 10–1 M/s 2. For the reaction C6H14(g) C6H6(g) + 4H2(g), P(H2)/t was found to be 2.5 × 10–2 atm/s, where P(H2) is the change in pressure of hydrogen. Determine P(C6H14)/t for this reaction at the same time. A) 2.5 × 10–2 atm/s B) –6.2 × 10–3 atm/s C) –2.5 × 10–2 atm/s D) 0.10 atm/s E) 6.2 × 10–3 atm/s 3. The reaction A + 2B products has the rate law, rate = k[A][B]3. If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase? A) 2 B) 4 C) 6 D) 8 E) 9 4. For the overall chemical reaction shown below, which one of the following statements can be rightly assumed? 2H2S(g) + O2(g) 2S(s) + 2H2O(l) A) The reaction is third-order overall. B) The reaction is second-order overall. C) The rate law is, rate = k[H2S]2 [O2]. D) The rate law is, rate = k[H2S] [O2]. E) The rate law cannot be determined from the information given. Page 1 5. The reaction A + 2B products was found to have the rate law, rate = k[A] [B]2. Predict by what factor the rate of reaction will increase when the concentration of A is doubled and the concentration of B is also doubled. A) 2 B) 4 C) 6 D) 8 E) 9 6. It takes 42.0 min for the concentration of a reactant in a first-order reaction to drop from 0.45 M to 0.32 M at 25°C. How long will it take for the reaction to be 90% complete? A) 13.0 min B) 86.0 min C) 137 min D) 222 min E) 284 min 7. Nitric oxide gas (NO) reacts with chlorine gas according to the chemical equation given below. 1 NO + 2 Cl2 NOCl The following initial rates of reaction have been measured for the given reagent concentrations. Expt. # Rate (M/hr) NO (M) Cl2 (M) 1 1.19 0.50 0.50 2 4.79 1.00 0.50 3 9.59 1.00 1.00 Which of the following is the rate law (rate equation) for this reaction? A) rate = k[NO] B) rate = k[NO][Cl2]1/2 C) rate = k[NO][Cl2] D) rate = k[NO]2[Cl2] E) rate = k[NO]2[Cl2]2 Page 2 8. Use the following data to determine the rate law for the reaction shown below. 2NO + H2 N2O + H2O Expt. # [NO]0 [H2]0 Initial rate 1 0.021 0.065 1.46 M/min 2 0.021 0.260 1.46 M/min 3 0.042 0.065 5.84 M/min A) rate = k[NO] B) rate = k[NO]2 C) rate = k[NO][H2] D) rate = k[NO]2[H2] E) rate = k[NO]2[H2]2 9. The half life for a first order reaction is 45 min. What is the rate constant in units of s-1? A) 0.015 s-1 B) 65 s-1 C) 2.6 x 10-4 s-1 D) 3.9 x 103 s-1 E) 1.9 x 103 s-1 10. The first-order decomposition, A products, has a rate constant of 0.150 s–1. Starting with [A]o = 0.350 M, how much time is required for [A]t = 0.125 M? A) 6.86 s B) 2.98 s C) 34 s D) 1.50 s E) 4.62 s 11. Appropriate units for a second-order rate constant are A) M/s B) 1/M·s C) 1/s D) 1/M2·s Page 3 12. The isomerization of cyclopropane to form propene is a first-order reaction. At 760 K, 15% of a sample of cyclopropane changes to propene in 6.8 min. What is the half-life of cyclopropane at 760 K? A) 3.4 × 10–2 min B) 2.5 min C) 23 min D) 29 min E) 230 min 13. At 700 K, the rate constant for the following reaction is 6.2 × 10–4 min–1. How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene? A) 1,120 min B) 360 min C) 3710 min D) 1.4 × 10–4 min E) 280 min 14. A reaction was experimentally determined to follow the rate law, Rate = k[A]2 where k = 0.456 s-1M-1. Starting with [A]o = 0.500 M, how many seconds will it take for [A]t = 0.250 M? A) 2.85 x 10-2 s B) 1.14 x 10-1 s C) 1.52 s D) 4.39 s E) 5.48x10-1 s 15. A reaction is experimentally found to follow the rate law, Rate = k[A]2 where k = 0.355 M-1min-1. Starting with [A]o = 1.55 M, how many seconds will it take for [A]t = 0.150M A) 6.58 s B) 395 s C) 6.02 s D) 17.0 s E) 1.02 x 103 s Page 4 16. The thermal decomposition of acetaldehyde, CH3CHO CH4 + CO, is a second-order reaction. The following data were obtained at 518°C. time, s Pressure CH3CHO, mmHg 0 364 42 330 105 290 720 132 Based on the data given, what is the half-life for the disappearance of acetaldehyde? A) 1.5 × 105 s B) 410 s C) 5.4 × 107 s D) 520 s E) 305 s 17. The graphs below all refer to the same reaction. What is the order of this reaction? A) B) C) D) zero order first order second order unable to predict 18. For what order reaction does the half-life get longer as the initial concentration increases? A) zero order B) first order C) second order D) none of them because half-life is always independent of the initial concentration 19. Which one of the following changes would alter the rate constant (k) for the reaction 2A + B products? A) increasing the concentration of A B) increasing the concentration of B C) increasing the temperature D) measuring k again after the reaction has run for a while Page 5 20. The Arrhenius equation is k = Ae–Ea/RT. The slope of a plot of ln k vs. 1/T is equal to A) –k B) k C) Ea D) –Ea /R E) A 21. What is the slope of an Arrhenius plot for the following reaction? 2NOCl 2NO + Cl2 Temperature (K) k (L/mol·s) 400. 6.6 × 10–4 500. 2.9 × 10–1 600. 16.3 –2 A) 8.18 × 10 K B) 5.06 × 10–2 K C) –1.22 × 104 K D) –1.96 × 104 K E) not enough information to calculate the slope 22. The isomerization of cyclopropane follows first order kinetics. The rate constant at 700 K is 6.20 × 10–4 min–1, and the half-life at 760 K is 29.0 min. Calculate the activation energy for this reaction. A) 5.07 kJ/mol B) 27.0 kJ/mol C) 50.7 kJ/mol D) 60. kJ/mol E) 270. kJ/mol 23. The reaction C4H10 C2H6 + C2H4 has an activation energy (Ea) of 350 kJ/mol, and the Ea of the reverse reaction is 260 kJ/mol. Estimate H, in kJ/mol, for the reaction as written above. A) –90 kJ/mol B) +90 kJ/mol C) 350 kJ/mol D) –610 kJ/mol E) +610 kJ/mol Page 6 24. Given that Ea for a certain biological reaction is 48 kJ/mol and that the rate constant is 2.5 × 10–2 s–1 at 15°C, what is the rate constant at 37°C? A) 2.7 × 10–2 s–1 B) 2.5 × 10–1 s–1 C) 1.0 × 10–1 s–1 D) 6.0 × 10–3 s–1 E) 1.1 s–1 25. For the chemical reaction system described by the diagram below, which statement is true? A) The forward reaction is endothermic. B) The activation energy for the forward reaction is greater than the activation energy for the reverse reaction. C) At equilibrium, the activation energy for the forward reaction is equal to the activation energy for the reverse reaction. D) The activation energy for the reverse reaction is greater than the activation energy for the forward reaction. E) The reverse reaction is exothermic. 26. The rate law for the reaction 2NO2 + O3 N2O5 + O2 is rate = k[NO2][O3]. Which one of the following mechanisms is consistent with this rate law? A) NO2 + NO2 N2O4 (fast) N2O4 + O3 N2O5 + O2 (slow) B) NO2 + O3 NO5 (fast) 5 NO5 + NO5 N2O5 + /2O2 (slow) C) NO2 + O3 NO3 + O2 (slow) NO3 + NO2 N2O5 (fast) D) NO2 + NO2 N2O2 + O2 (slow) N2O2 + O3 N2O5 (fast) Page 7 27. The peroxodisulfate ion can oxidize iodide ions to iodine according to the balanced equation S2O82– + 2I – 2SO42– + I2. The reaction is catalyzed by certain chemical species. Identify the catalyst in the following mechanism: step 1: Fe3+ + 2I – Fe2+ + I2 step 2: S2O82– + Fe2+ 2SO42– + Fe3+ A) Fe3+ B) I – C) S2O82– D) Fe2+ E) SO42– 28. At a particular temperature the first-order gas-phase reaction N2O5 2NO2 + 1/2O2 has a half-life for the disappearance of dinitrogen pentoxide of 5130 s. Suppose 0.450 atm of N2O5 is introduced into an evacuated 2.00 L flask. What will be the total gas pressure inside the flask after 3.00 hours? A) 0.969 atm B) 0.105 atm C) 0.795 atm D) 1.14 atm E) 0.864 atm Page 8 Answer Key 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. B B D E D E D B C A B D B D E B A A C D C E B C D C A A Page 9