MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Transcription

1 Chemistry 213 Exam I - A Spring 2010 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN): 1) CH3NC (g) CH3CN (g) The reaction is first order in methylisonitrile. The attached graph shows data for the reaction obtained at C. The rate constant for the reaction is s-1. A) B) C) D) +6.2 E) ) A catalyst can increase the rate of a reaction. 2) A) by lowering the activation energy of the reverse reaction B) by increasing the overall activation energy (Ea) of the reaction C) by providing an alternative pathway with a lower activation energy D) by changing the value of the frequency factor (A) E) All of these are ways that a catalyst might act to increase the rate of reaction. 3) What order process is radioactive decay? 3) A) zeroth B) first C) second D) third E) fourth 1

2 4) A second-order reaction has a half-life of 18 s when the initial concentration of reactant is 0.71 M. The rate constant for this reaction is M-1s-1. A) B) 18 C) D) E) 1.3 4) 5) Alpha decay produces a new nucleus whose than those respectively of the original nucleus. A) atomic number is 2 less and mass number is 4 less B) atomic number is 1 less and mass number is 2 less C) atomic number is 2 more and mass number is 2 less D) atomic number is 2 less and mass number is 2 less E) atomic number is 2 more and mass number is 4 more 6) At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN): 5) 6) CH3NC (g) CH3CN (g) The dependence of the rate constant on temperature is studied and the graph below is prepared from the results. The energy of activation of this reaction is kj/mol. A) B) C) 160 D) E)

3 7) The mechanism for formation of the product X is: 7) A + B C + D B + D X (slow) (fast) The intermediate reactant in the reaction is. A) A B) B C) C D) D E) X 8) The initial concentration of reactant in a first-order reaction is 0.27 M. The rate constant for the reaction is 0.75 s-1. What is the concentration (mol/l) of reactant after 1.5 s? A) 3.8 B) C) D) E) 1.7 8) The data in the table below were obtained for the reaction: A + B P Experiment Number [A] (M) [B] (M) Initial Rate (M/s) ) The order of the reaction in B is. 9) A) 1 B) 2 C) 3 D) 4 E) 0 3

4 10) 131I has a half-life of 8.04 days. Assuming you start with a 1.53 mg sample of 131I, how many mg will remain after 13.0 days? A) B) C) D) E) ) 11) The graph shown below depicts the relationship between concentration and time for the following chemical reaction. 11) The slope of this line is equal to. A) ln[a]o B) k C) -k D) 1/k E) -1/k 12) Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction? 12) A) x B) y C) y - x D) x - y E) x + y 4

5 13) Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction: 13) 2NO2 2NO + O2 In a particular experiment at 300 C, [NO2] drops from to M in 100 s. The rate of appearance of O2 for this period is M/s. A) B) C) D) E) ) The rate of a reaction depends on. 14) A) collision frequency B) collision energy C) collision orientation D) all of the above E) none of the above 15) A reaction was found to be zero order in A. Increasing the concentration of A by a factor of 3 will cause the reaction rate to. A) decrease by a factor of the cube root of 3 B) increase by a factor of 27 C) remain constant D) increase by a factor of 9 E) triple 15) 16) The rate law for a reaction is 16) rate = k [A][B]2 Which one of the following statements is false? A) The reaction is first order in A. B) If [B] is doubled, the reaction rate will increase by a factor of 4. C) k is the reaction rate constant D) The reaction is second order overall. E) The reaction is second order in B. 5

6 17) In general, as temperature goes up, reaction rate. 17) A) goes up if the reaction is exothermic B) stays the same regardless of whether the reaction is exothermic or endothermic C) goes up if the reaction is endothermic D) stays the same if the reaction is first order E) goes up regardless of whether the reaction is exothermic or endothermic 18) This reaction is an example of. 18) Po Pb + 82 A) positron emission B) beta emission C) gamma emission D) electron capture E) alpha decay 19) The rate constant for a particular second-order reaction is 0.47 M-1s-1. If the initial concentration of reactant is 0.25 mol/l, it takes s for the concentration to decrease to 0.13 mol/l. A) 3.7 B) 1.4 C) 1.7 D) 0.13 E) ) 20) As the temperature of a reaction is increased, the rate of the reaction increases because the. A) reactant molecules collide less frequently B) reactant molecules collide more frequently and with greater energy per collision C) reactant molecules collide less frequently and with greater energy per collision D) reactant molecules collide more frequently with less energy per collision E) activation energy is lowered 20) 6