CH Practice Exam #4 (Fall 2017) - Answers

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1 H Practice Exam #4 (Fall 2017) - nswers Name: Part I (~5 points each) Score: Multiple hoice - hoose the best answer and place the letter corresponding to the answer in the space provided N on the Scantron form. 1. For the following balanced equation, determine the rate of reaction with respect to [H2]. N2(g) + 3 H2(g) 2 NH3(g) ) Rate = + 3 Δ[H2] ) Rate = - 1 Δt 3 1 Δ[H2] Δt E ) Rate = + 1 Δ[H2] ) Rate = - 3 Δt 2. Give the characteristic of a first order reaction having only one reactant. ) The rate of the reaction is not proportional to the concentration of the reactant. ) The rate of the reaction is proportional to the square of the concentration of the reactant. ) The rate of the reaction is proportional to the square root of the concentration of the reactant. ) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant. E) The rate of the reaction is directly proportional to the concentration of the reactant 3. What is the overall order of the following reaction, given the rate law? 1 3 Δ[H2] Δt X + 2 Y 4 Z Rate = k[x][y] ) 3rd order ) 5th order ) 2nd order ) 1st order E) 6th order 4. What are the units of k in the following rate law? Rate = k[x][y]1/2 ) M/s ) M -1 s -1 ) M 1/2 s -1 ) M -1/2 s -1 E) M -1 s -1/2

2 5. Which of the following statements is FLSE? ) The half life of a zero order reaction is dependent on concentration. ) The half life of a second order reaction is not dependent on concentration. ) The rate of second order reactions is dependent on concentration. ) The rate of a first order reaction is dependent on concentraion. E) None of the statements are FLSE. 6. The half life for the decay of radium is 1620 years. What is the rate constant for this firstorder process? ) yr -1 ) yr -1 ) y -1 ) y -1 E) yr Identify an heterogeneous catalyst. ) Fs with ozone ) Pd in H2 gas ) KI dissolved in H2O2 ) H2SO4 with concentrated Hl E) H3PO4 with an alcohol 8. Given the following rate law, how does the rate of reaction change if the concentration of Y is doubled? Rate = k [X][Y]2 ) The rate of reaction will increase by a factor of 2. ) The rate of reaction will increase by a factor of 4. ) The rate of reaction will increase by a factor of 5. ) The rate of reaction will decrease by a factor of 2. E) The rate of reaction will remain unchanged. 9.How many half-lives are required for the concentration of reactant to decrease to 12.5% of its original value? ) 3 ) 2 ) 2.5 ) 2.75 E) 8

3 10. The combustion of ethylene proceeds by the reaction 2 H 4 (g) + 3O 2 (g) 2O 2 (g) + 2H 2 O(g) When the rate of disappearance of O 2 is 0.28 M s-1, the rate of appearance of O 2 is M s-1. ) 0.19 ) ) 0.84 ) 0.42 E) etermine the identity of the daughter nuclide from the alpha decay of ) 218 Po ) 88 Ra 224 ) 90Th 223 ) 86 Rn 221 E) 85 t 12. etermine the identity of the daughter nuclide from the electron capture by ) o 27 ) Mn 25 ) 56 o 27 ) 54 Mn 25 E) 51 r The following reaction represents what nuclear process? Pb -1 e 83 i 222 Rn. 86 Fe. 26 ) beta emission ) positron emission ) gamma emission ) electron capture 14. Which of the following nuclides are most likely to decay via positron emission? ) s-137 ) I-131 ) l-24 ) K-42 E) N-14

4 Part II (~8 points each) - Show all of your calculations for full credit. 1. etermine the rate law and the value of k for the following reaction using the data provided. S2O8 2 (aq) + 3 I (aq) 2 SO4 2 (g) + I3 (aq) ) Rate = 120 M-2s-1 [S2O8 2 ]2[I ] ) Rate = 36 M-1s-1 [S2O8 2 ][I ] ) Rate = 86 M-2s-1 [S2O8 2 ][I ]2 ) Rate = 195 M-3s-1 [S2O8 2 ]2[I ]2 E) Rate = 23 M-1/2s-1 [S2O8 2 ][I ]1/2 [S2O8 2 ]i (M) [I ]i (M) Initial Rate (M-1s-1) The first-order decomposition of N2O at 1000 K has a rate constant of 0.76 s-1. If the initial concentration of N2O is 10.9 M, what is the concentration of N2O after 9.6 s? ) M ) M ) M ) M E) M 3. The first-order rearrangement of H3N is measured to have a rate constant of 3.61 x s-1 at 298 K and a rate constant of s-1 at 425 K. etermine the activation energy for this reaction. ) 160. kj/mol ) 240. kj/mol ) 417 kj/mol ) 127 kj/mol E) 338 kj/mol

5 4. The age of an ancient tree trunk is estimated using radiocarbon dating. If the trunk has a -14 decay rate that is 34% of what it is in living plants, how old is the trunk? The half-life of -14 is 5730 years. ) years ) years ) years ) years E) years 5. etermine the binding energy per nucleon of an Mg-24 nucleus. The Mg-24 nucleus has a mass of proton has a mass of amu, a neutron has a mass of amu, and 1 amu is equivalent to 931 MeV of energy. ) MeV ) 8.83 MeV ) MeV ) 106 MeV E) 4.41 MeV

CH Practice Exam #3 -

CH Practice Exam #3 - CH1810 - Practice Exam # - Name: Score: Part I (~ points each) Multiple Choice - Choose the best answer and place the letter corresponding to the answer in the space provided AND on the Scantron form.