6.9 Practice Problems

Attempt these problems as if they were real exam questions in an exam environment.

Only look up information if you get severely stuck. Never look at the solution until you have exhausted all efforts to solve the problem.


  1. If [H2] = 0.5 and [I2] = 0.5, initially, for the following reaction at 400 °C,

    \[\mathrm{H_2}(g) + \mathrm{I_2}(g) \rightleftharpoons 2\mathrm{HI}(g) \quad K = 64.0\]

    what is [HI] (in M) at equilibrium?

    1. 0.2
    2. 0.4
    3. 0.8
    4. 1.2
    5. 4.6

    Solution


  2. What is Kp for the following reaction at 5 °C?

    \[\mathrm{N_2O_4}(g) \rightleftharpoons \mathrm{2NO_2}(g) \quad K = 15\]

    1. 15.0
    2. 289.6
    3. 6.2
    4. 367.0
    5. 342.4

    Solution


  3. What is Kp for the following reaction at 25 °C?

    \[\mathrm{NO_2}(g) \rightleftharpoons \mathrm{N_2O_4}(g) \quad K = 215.98\]

    1. 8.83
    2. 12.23
    3. 443.09
    4. 5.28 × 103
    5. 5.35 × 105

    Solution


  4. A solution initially contains 0.55 M of A and B. The following balanced reaction occurs and the equilibrium concentration for B is found to be 0.21 M. What is K for this reaction?

    \[\mathrm{A}(aq) + \mathrm{B}(aq) \rightleftharpoons \mathrm{2C}(aq)\]

    1. 0.12
    2. 0.25
    3. 3.5
    4. 6.8
    5. 10.5

    Solution


  5. A reaction is found to be proceeding left towards equilibrium at a particular point in the reaction. Pick the true statement.

    1. Q = K
    2. Q > K
    3. Q < K
    4. ratef = rater
    5. none of these

    Solution


  6. The following reaction is carried out in a 1.0 L vessel:

    \[\mathrm{SO_2}(g) + \mathrm{H_2O}(g) \rightleftharpoons \mathrm{H_2SO_3}(g) \quad K = 0.115\]

    What is the mass (in g) of the product at equilibrium if there is 40.0 g of SO2 (m.m. = 64.066 g mol–1) and 100.0 g of H2O at equilibrium?

    1. 20
    2. 33
    3. 60
    4. 80
    5. 100

    Solution


  7. Which statement is true regarding chemical equilibrium?

    1. The rates of the forward and reverse reactions are equal and remain constant
    2. Concentrations of reactants and products are equal and remain constant
    3. The rates of the forward and reverse reactions are not equal but remain constant
    4. The forward and reverse reactions have stopped
    5. none of these

    Solution


  8. Pick the false statement regarding the following reaction at equilibrium.

    \[\mathrm{H_2}(g) + \mathrm{I_2}(g) \rightleftharpoons 2\mathrm{HI}(g) \quad \Delta H > 0\]

    1. Lowering the temperature drives the reaction right
    2. Adding H2 drives the reaction right
    3. Removing HI drives the reaction right
    4. For every 1 mol of H2 consumed, 2 mol HI is produced
    5. Decreasing P has no effect on the reaction direction

    Solution


  9. Which action will drive the following endothermic reaction toward the right?

    \[2\mathrm{PbS}(s) + \mathrm{3O_2}(g) \rightleftharpoons \mathrm{2PbO}(s) + 2\mathrm{SO_2}(g)\]

    1. addition of heat
    2. removal of heat
    3. addition of PbS
    4. removal of O2
    5. none of these

    Solution


  10. What is the equilibrium constant for the reverse of the following reaction?

    \[\mathrm{A}+\mathrm{2B} \longrightarrow \mathrm{3C} \qquad K = 1.40 \times 10^{-3}\]

    1. –1.40 × 10–3
    2. 1.40 × 10–3
    3. 1.0
    4. 714.3
    5. 2.80 × 103

    Solution