Equilibrium Test


True/False

  1. Chemical equilibrium is explained by dynamic molecular behavior resulting in a balanced opposing reaction.

  2. A burning candle reaches an identifiable state of chemical equilibrium.

  3. Temperature almost never influences the equilibrium of a reaction.

  4. For the reaction, m A + n B p C + q D, the numerator of the equilibrium constant is [C]p [D]q

  5. Increasing the temperature of the reaction, H2O (g) + C (s) + 31.4 Kcal CO (g) + H2 (g), would be a way to make more products.

  6. Using the reaction given in problem 5, increasing the amount of CO would shift the reaction to the right.

  7. The value of the equilibrium constant, Keq, for a specific reaction depends on the temperature.

  8. A catalyzed reaction usually produces more products than an uncatalyzed reaction.

  9. If the solubility of PbCrO4 is 1.0 x 10 -4, the Ksp is 1.0 x 10 -2.

  10. Equilibrium tends to favor the side of the reaction with the least amount of randomness.

Multiple Choice (Choose the best answer.)

  1. Reactions that proceed in both the forward and reverse directions are said to be

    complete.

    static.

    balanced.

    reversible.

    none of these.

  2. You studied the reaction, Fe3+ + SCN- FeSCN2+ + Energy. Which of the following would shift the equilibrium to the reactants?

    Inrease [ Fe3+].

    Remove energy.

    Decrease [SCN-].

    Add energy.

    More than one of these would shift the equilibrium left.

  3. What would be the result of increasing the pressure by decreasing the volume on the reaction:

    4 NH3 (g) + 5 O2 (g) 4 NO (g) + 6 H2O (g)

    The equilibrium would shift to the products.

    The equilibrium would shift to the reactants.

    The equilibrium would shift both directions.

    The equilibrium would not change.

    It is impossible to tell with the information given.

  4. An equilibrium constant much larger than one indicates:

    a reaction that makes lots of products.

    a reaction that does not make many products.

    a reaction that reaches equilibrium quickly.

    a reaciton that takes a long time to reach equilibrium.

    a reaction that does not achieve equilibrium.

  5. In the following reaction at equilibrium, the concentration of each substance is [ A ] = 2 M; [B] = 2 M; [C] = 2 M; [D] = 1 M. What is the value of Keq, (the equilibrium constant)?

    2 A + B 3 C + 2 D

    0.50

    0.75

    1.0

    1.3

    5.0

  6. If in the reaction in problem 5 "A" and "C" were both solids, while "B" and "D" were both aqueous, the value of the equilibrium constant wold be:

    0.50

    0.75

    1.0

    1.3

    5.0

  7. The Ksp expression for the reaction BaF2(s) dissolving ( BaF2(s) Ba2+ (aq) + 2 F- (aq) ) woud be:

    Ksp = [Ba2+][F-]2

    Ksp = [Ba2+][2 F-]2

    Ksp =[Ba2+][2 F-]

    Ksp = [Ba2+][F-]2 / [BaF2]

    Ksp = [BaF2] / {[Ba2+][F-]2}

  8. If the Ksp for the reaction in 7 was 1.0 x 10 -6, the solubility of BaF2 (s) is:

    1.0 x 10 -6

    1.0 x 10 -3

    6.3 x 10 -3

    1.0 x 10 -2

    None of these.

  9. Which of these has more randomness?

    Ice at -50 oC.

    Ice at 0 oC

    Liquid water at 25 oC

    Steam at 100oC

    Steam at 150 oC

  10. Examine the reaction, 3 H2 (g) + N2 (g) 2 NH3 (g) + 22 Kcal, in terms of enthalpy (energy) and entropy (randomness).

    Energy favors products while randomness favors reactants.

    Energy favors products and randomness favors products.

    Energy favors reactants and randomness favors reactants.

    Energy favors reactants while randomness favors products.

    It is impossible to analyze the reaction with the information given.

Problem Solving (Respond in complete sentences. Use correct spelling and grammar.)


The questions below are based on the following reaction, which takes place in a closed container:

NO (g) + NO2 (g) N2O3 (g) + 9.6 Kcal

1) How does the rate of the forward reaction compare with the rate of the reverse reaction at equilibrium?




2) What is the effect on the partial pressure of N2O3 if some NO (g) is added after the system has reached equilibrium?




3) What effect does a catalyst have on the rate of the forward and reverse reactions? Explain.




4) Compare the equilibrium concentration of N2O3 (g) without a catalyst to its equilibrium concentration with a catalyst, Explain.




5) Discuss the effects of randomness (entropy) and potential energy (enthalpy) on the value of the equilibrium constant. Can you predict whether the reaction will have a large or small value for K?

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