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5 Written questions

5 Matching questions

  1. Assume the following reaction occurs by the given reaction mechanism.
    3H2 + CO → CH4 + H2O

    Step 1 H2 + CO → H2CO slow
    Step 2 H2 + H2CO → CH4 + O fast
    Step 3 H2 + O → H2O fast
    Overall 3H2 + CO → CH4 + H2O

    The rate law expression must be rate = ____.
    a. k[H2]2[CO]2
    b. k[H2]2[CO]
    c. k[H2][CO]2
    d. k[H2][CO]
    e. k[H2]2[CO]3
  2. 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]
  3. The gas-phase reaction
    2NO + 2H2 → N2 + 2H2O
    has the following rate law expression, rate = k[NO]2[H2]. If the [NO] is halved and the [H2] is tripled, what change in rate is expected?
    a. decrease by 3/4
    b. increase by 3/4
    c. increase by 3/2
    d. decrease by 3/2
    e. stays same
  4. What would be the activation energy of a reaction if its rate constant at 35°C was double the value of its rate constant at 25°C?
    a. 63.8 kJ/mol
    b. 75.1 kJ/mol
    c. 8.12 kJ/mol
    d. 52.9 kJ/mol
    e. 68.3 J/mol
  5. The rate constant for a first-order reaction is 1.4 × 10-2 s-1 at 716 K and 5.5 × 10-2 s-1 at 864 K. What is the activation energy?
    a. 27 kJ/mol
    b. 21 kJ/mol
    c. 47 kJ/mol
    d. 5700 kJ/mol
    e. 48 kJ/mol
  1. a d. 52.9 kJ/mol
  2. b a. decrease by 3/4
  3. c d. k[H2][CO]
  4. d c. rate = k1[A]2
  5. e e. 48 kJ/mol

5 Multiple choice questions

  1. a. Zero order
  2. c. 5.5 min
  3. c. first order in A and first order in C2
  4. -DeltaA/Dt
  5. c. Rate = k[A][B]

5 True/False questions

  1. The decomposition of dinitrogen pentoxide obeys the rate-law expression rate = 0.080 min−1[N2O5]. If the initial concentration of N2O5 is 0.30 M, what is the concentration after 2.6 minutes?
    N2O5 → N2O3 + O2

    a. 0.38 M
    b. 0.028 M
    c. 0.24 M
    d. 0.13 M
    e. 0.32 M
    a. 3.10 hrs


  2. The gas phase reaction below obeys the rate-law expression rate = k[SO2Cl2]. At 593 K the specific rate constant is 2.2 × 10−5 s−1. A 2.0-g sample of SO2Cl2 is introduced into a closed 4.0-L container.
    SO2Cl2 → SO2 + Cl2

    How much time must pass in order to reduce the amount of SO2Cl2 present to 1.8 grams?
    a. 7.4 × 103 seconds
    b. 2.1 × 102 seconds
    c. 3.5 × 102 seconds
    d. 4.8 × 103 seconds
    e. 5.8 × 104 seconds
    d. 4.8 × 103 seconds


  3. Which statement is false?
    a. If a reaction is thermodynamically spontaneous, it may occur rapidly.
    b. A fast reaction may be thermodynamically spontaneous.
    c. If a reaction is thermodynamically spontaneous, it may occur slowly.
    d. If a reaction is thermodynamically spontaneous, it must have a low activation energy.
    e. Rate of reaction is a kinetic quantity rather than a thermodynamic quantity.
    b. The specific rate constant for a zero-order reaction is independent of temperature.


  4. Which of the following statements regarding temperature and reaction rate is false.
    a. The Arrhenius equation can be used to find the activation energy of a reaction.
    b. Reaction rate always increases with higher temperature.
    c. A larger negative value of ΔG0 causes a faster reaction rate.
    d. A larger value of Ea causes a slower reaction rate.
    e. The rate constant for a reaction decreases at lower temperatures.
    d. the reaction of leaded fuels with the catalysts in catalytic converters


  5. Suppose the reaction
    2AB + C2 → A2C + B2C
    occurs by the following mechanism.

    Step 1 AB + C2 → AC2 + B slow
    Step 2 B + AB → AB2 fast
    Step 3 AC2 + AB2 → A2C2 + B2 fast
    Step 4 A2C2 + B2 → A2C + B2C fast
    Overall 2 AB + C2 → A2C + B2C

    The rate law expression must be rate = ____.
    a. k[AB][C2]
    b. k[AB]2[C2]
    c. k[AB]2
    d. k[AB]
    e. k[C2]
    a. k[AB][C2]