Review Questions

  1. All of the following are true statements concerning reaction orders EXCEPT:

    1. The rate of a zero-order reaction is constant.
    2. After three half-lives, a radioactive sample will have one-ninth of its original concentration.
    3. The units for the rate constant for first-order reactions are s−1.
    4. If doubling the concentration of a reactant doubles the rate of the reaction, then the reaction is first order in that reactant.

  2. The half-life of radioactive sodium is 15.0 hours. How many hours would it take for a 64 g sample to decay to one-eighth of its original concentration?

    1. 3
    2. 15
    3. 30
    4. 45

  3. Consider the following hypothetical reaction and experimental data:

    [A]0 (mol/L) [B]0 (mol/L) Rate
    Exp 1 0.10 1 0.035
    Exp 2 0.10 4 0.070
    Exp 3 0.20 1 0.140
    Exp 4 0.10 16 0.140
    1. What is the order with respect to A?
    2. What is the order with respect to B?
    3. What is the rate equation?
    4. What is the overall order of the reaction?
    5. Calculate the rate constant.

  4. Consider the following chemical reaction and experimental data:

    A (aq) → B (aq) + C(g)
    Trial 1 Trial 2
    [A] (mol/L) Rate [A] (mol/L) Rate
    0.10 0.6 0.10 0.9
    0.20 0.6 0.20 0.9
    0.30 0.6 0.30 0.9
    0.40 0.6 0.40 0.9
    1. What is the rate expression for trial 1?
    2. What is the rate constant for trial 1?
    3. What is the most likely reason for the increased rate in trial 2?

  5. Consider the following reaction and experimental data:

    SO3 + H2O → H2SO4
    [SO3] (mol/L) [H2O] (mol/L) Rate
    Trial 1 0.1 0.01 0.013
    Trial 2 0.2 0.01 0.052
    Trial 3 X 0.02 0.234
    Trial 4 0.1 0.03 0.039
    1. What is the value of X?
    2. What is the order of the reaction?
    3. What is the rate constant?
    4. What would be the rate if [SO3] in trial 4 were raised to 0.2?

  6. In the following diagram, which labeled arrow represents the activation energy for the reverse reaction?

    1. A
    2. B
    3. C
    4. D

  7. The activation energy for a reaction in the forward direction is 78 kJ. The activation energy for the same reaction in reverse is 300 kJ. If the energy of the products is 25 kJ, then:

    1. What is the energy of the reactants?
    2. Is the forward reaction endothermic or exothermic?
    3. Is the reverse reaction endothermic or exothermic?
    4. What is the enthalpy change for the forward reaction?

  8. According to chemical kinetic theory, a reaction can occur

    1. if the reactants collide with the proper orientation
    2. if the reactants possess sufficient energy of collision
    3. if the reactants are able to form a correct transition state
    4. All of the above

  9. The number of undecayed nuclei in a sample of bromine-87 decreased by a factor of 4 over a period of 112 s. What is the rate constant for the decay of bromine-87?

    1. 56 s
    2. 6.93 × 10−1 s−1
    3. 1.24 × 10−2 s−1
    4. 6.19 × 10−3 s−1

  10. Which of the following is most likely to increase the rate of a reaction?

    1. Decreasing the temperature
    2. Increasing the volume of the reaction vessel
    3. Reducing the activation energy
    4. Decreasing the concentration of the reactant in the reaction vessel

  11. All of the following are true statements concerning catalysts EXCEPT

    1. A catalyst will speed the rate-determining step.
    2. A catalyst will be used up in a reaction.
    3. A catalyst may induce steric strain in a molecule to make it react more readily.
    4. A catalyst will lower the activation energy of a reaction.

  12. The equilibrium constant, Keq, of a certain single-reactant reaction is 0.16. Suppose an appropriate catalyst is added.

    1. What will be the equilibrium constant?
    2. Will the activation energy increase or decrease?

  13. At equilibrium

    1. the forward reaction will continue
    2. a change in reaction conditions may shift the equilibrium
    3. the reverse reaction will not continue
    4. Both A and B