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5 Written questions

5 Matching questions

  1. 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
  2. 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]
  3. 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
  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]
  5. 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
  1. a a. increasing the temperature
  2. b a. k[AB][C2]
  3. c b. 300°K
  4. d c. Rate = k[A][B]
  5. e a. 0.068 M•s−1

5 Multiple choice questions

  1. b. second; first
  2. a. 3.10 hrs
  3. b. 0.075 mol/L•min
  4. a. I
  5. a. 21 min

5 True/False questions

  1. One of the reactions that is used to produce gaseous hydrogen commercially follows. A proper expression for the rate of this reaction could be ____.
    H2O(g) + CO(g) → H2(g) + CO2(g)

    c. k


  2. Which statement concerning a possible mechanism for a reaction is false?
    a. A possible mechanism must be consistent with the experimental data.
    b. Each elementary step is represented by a balanced equation.
    c. The elementary steps must add to give the equation for the overall reaction.
    d. The speed of the slow step limits the rate at which the overall reaction occurs.
    e. The slow step will only include reactants listed in the overall chemical equation.
    e. The slow step will only include reactants listed in the overall chemical equation.


  3. 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
    d. k[H2][CO]


  4. Which is not an example of the effect of subdivision of the reactant on the rate of chemical reaction?
    a. Violent explosions that occur in grain elevators.
    b. A container of flammable liquid will burn on the surface but allowed to vaporize will burn explosively.
    c. A chunk of iron takes months to rust completely while iron wool will rust in days.
    d. Some metals may be fused (welded) with minimal loss while their powders will burn in a flame.
    e. The Grand Canyon was created by dissolution by water over millions of years.
    c. Magnesium reacts faster in higher concentrations of HCl(aq).


  5. For a certain third-order reaction with the general form aA → products, the rate is 0.36 M·s−1 when the concentration of the reactant is 0.35 mol/L. What is the rate constant for this reaction?

    a. 0.042 M−2⋅s−1
    b. 8.4 M−2⋅s−1
    c. 0.36 M−2⋅s−1
    d. 0.34 M−2⋅s−1
    e. 24 M−2⋅s−1
    a. second