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5 Written questions

5 Matching questions

  1. The rate constant for a first-order reaction is 0.58 s−1 at 25°C. At what temperature would the rate constant have a value of 0.75 s−1? The activation energy is 84 kJ/mol and the universal gas constant = 8.314 J/mol•K.


    a. 30°C
    b. 300°K
    c. 298 K
    d. 301 K
    e. 310 K
  2. The gas-phase reaction
    2NO + 2H2 → N2 + 2H2O
    has the following rate law expression, rate = 0.14 L2/mol2•s[NO]2[H2]. If the [NO] is 0.95 M and the [H2] is 0.45 M, what rate is expected?
    a. 0.060 mol/L•s
    b. 0.43 mol/L•s
    c. 0.027 mol/L•s
    d. 1.54 mol/L•s
    e. 0.057 mol/L•s
  3. Which of the following statements regarding the rate constant in the rate law expression is incorrect?
    a. Its value increases with temperature.
    b. Its value is independent of initial concentration at a given temperature.
    c. Its units depend on the overall order of reaction.
    d. Its value is experimentally determined.
    e. The larger its value, the slower the reaction rate.
  4. The reaction below has the following rate law: rate = 0.011 L/mol•s [SF4]2.
    SF4 → SF2 + F2

    How many minutes will it take for the concentration of SF4 to be reduced from 2.5 M to 0.25 M?
    a. 327 min
    b. 0.025 min
    c. 5.5 min
    d. 0.040 min
    e. 22.7 min
  5. For a certain reaction of the general form aA → products, a plot of the experimental data as 1/[A] versus time is linear. What is the reaction order with respect to reactant A?
    a. second
    b. zero
    c. first
    d. fourth
    e. third
  1. a b. 300°K
  2. b e. The larger its value, the slower the reaction rate.
  3. c e. 0.057 mol/L•s
  4. d c. 5.5 min
  5. e a. second

5 Multiple choice questions

  1. a. increasing the temperature
  2. e. a greater fraction of molecules possess the activation energy when they collide
  3. a. Zero order
  4. a. 1.7 s
  5. c. Each enzyme catalyzes many different reactions in a living system.

5 True/False questions

  1. Consider the following proposed mechanism. If this mechanism for the overall reaction were correct, and if k1 were much less than k2, then the observed rate law would be
    2A C + I
    I + B C + D

    a. rate = k1[A]
    b. rate = k2[I][B]
    c. rate = k1[A]2
    d. rate = k1[A]2 − k2[C][D]
    e. rate = k1k2[A]2[I][B]
    c. rate = k1[A]2

          

  2. 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. rate = k1[A]2

          

  3. 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.
    e. Reactions involving simultaneous trimolecular collisions are very common in gases.

          

  4. Consider the hypothetical reaction shown below.
    A + 2B → AB2

    Assume that the following proposed mechanism is consistent with the rate data.

    B + B → B2 slow
    B2 + A → AB + B fast
    B + AB → AB2 fast
    A + 2B → AB2 overall

    Which one of the following statements must be true? The reaction is ____.
    a. first order in A, second order in B, and third order overall
    b. second order in B and second order overall
    c. first order in A and first order overall
    d. second order in B, zero order in A, and third order overall
    e. second order in A and second order overall
    c. rate = k[NH4+][NO2−]2

          

  5. A hypothetical reaction X + 2Y → Products is found to be first order in X and second order in Y. What are the units of k, the specific rate constant, if reaction rate is expressed in units of moles per liter per second?
    a. M•s−1
    b. M−2•s−1
    c. M−3•s
    d. M2•s−1
    e. M−1•s
    b. M−2•s−1

          

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