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5 Written questions

5 Matching questions

  1. The specific rate constant, k, for a reaction is 0.44 s−1 at 298 K, and the activation energy is 245.kJ/mol. Calculate k at 398 K. (The universal gas constant = 8.314 J/mol•K.)


    a. 2.71 × 1010 s−1
    b. 6.17 × 1010 s−1
    c. 1.03 × 1010 s−1
    d. 8.32 × 108 s−1
    e. 4.51 × 109 s−1
  2. The rate constant, k, for a first-order reaction is 1.36 × 103 s−1 at 90.°C and the activation energy is 78.4 kJ/mol. Calculate the rate constant for this reaction at 50.°C.
    a. 60.4 s−1
    b. 54.5 s−1
    c. 23.8 s−1
    d. 4.85 s−1
    e. 1.78 × 103 s−1
  3. The gas phase reaction A + B → C has a reaction rate which is experimentally observed to follow the relationship rate = k[A]2[B]. Which one of the following would affect the value of the specific rate constant, k?
    a. increasing the temperature
    b. changing the concentration of A
    c. changing the concentration of B
    d. changing the concentration of C
    e. all of these
  4. Which of the following statements concerning graphical methods for determining reaction order is false?
    a. For a first-order reaction the plot of ln[A] vs. time gives a straight line.
    b. For a first-order reaction the slope of the straight-line graph equals −ak.
    c. For a second-order reaction the plot of [A]2 vs. time gives a straight line.
    d. For a first-order reaction the intercept of the straight-line graph equals ln [A]0.
    e. For a zero-order reaction the plot of [A] vs. time gives a straight line.
  5. 124 go to graph
  1. a go to graph
  2. b b. 54.5 s−1
  3. c a. increasing the temperature
  4. d a. 2.71 × 1010 s−1
  5. e c. For a second-order reaction the plot of [A]2 vs. time gives a straight line.

5 Multiple choice questions

  1. d. 52.9 kJ/mol
  2. e. k[A][B]2
  3. b. The specific rate constant for a zero-order reaction is independent of temperature.
  4. d. 1 and 2
  5. b. 0.00648 M

5 True/False questions

  1. The oxidation of NO by O3 is first order in each of the reactants, and its rate constant is 1.5 × 107 M−1•s−1. If the concentrations of NO and O3 are each 5.0 × 10−7 M, what is the rate of oxidation of NO in M•s−1?
    a. 3.8 × 10−6
    b. 2.5 × 10−14
    c. 7.5 × 10−7
    d. 15
    e. 7.5
    a. 3.8 × 10−6

          

  2. Which of the following statements about reaction mechanisms is false?
    a. A reaction can have more than one possible mechanism.
    b. A reaction mechanism must be consistent with the experimentally observed rate law.
    c. The slowest step in the reaction mechanism is called the rate-determining step.
    d. Reaction mechanisms involve complex reaction steps.
    e. Reaction mechanisms are difficult to prove.
    d. Reaction mechanisms involve complex reaction steps.

          

  3. A catalyst ____.
    a. is used up in a chemical reaction
    b. changes the value of ΔG0 of the reaction
    c. is always a solid
    d. does not influence the reaction in any way
    e. changes the activation energy of the reaction
    e. changes the activation energy of the reaction

          

  4. The reaction, A + 2B → B2 + A, proceeds by the following mechanism: (A is a catalyst.)
    A + B → AB (slow)
    AB + B → B2 + A (fast)

    What is the rate law expression for this reaction?
    a. Rate = k[A]
    b. Rate = k[B]
    c. Rate = k[A][B]
    d. Rate = k[A][B]2
    e. Rate = k[A]2[B]
    c. Rate = k[A][B]

          

  5. Rate data have been determined at a particular temperature for the overall reaction
    2NO + 2H2 → Ν2 + 2H2O
    in which all reactants and products are gases.

    Trial Run Initial [NO] Initial [H2] Initial Rate (M•s−1)
    1 0.10 M 0.20 M 0.0150
    2 0.10 M 0.30 M 0.0225
    3 0.20 M 0.20 M 0.0600

    What would be the initial rate of the reaction if the initial molar concentration of NO = 0.30 M and the initial molar concentration of H2 = 0.10 M?
    a. 0.068 M•s−1
    b. 0.22 M•s−1
    c. 0.022 M•s−1
    d. 0.040 M•s−1
    e. 0.10 M•s−1
    c. A larger negative value of ΔG0 causes a faster reaction rate