Equilibrium Practice Test

 

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  1. Consider:

    Br 2 (l) + Cl2 (g)→ 2BrCl (g)

    4.00 moles of chlorine and 2.00 moles of bromine are placed in a 50.0L container and kept at 293K until equilibrium is reached.  At equilibrium there are 82.63g of Br2 (l).  Determine the total pressure in the 50.0L container at equilibrium.

    2.  

     

  2. Consider the following endothermic reaction:

    2 Na(s) + Cl2 (g)  2 NaCl (aq)

    In which direction would the reaction shift for the following:
    • Na was added to the mixture
    • The temperature lowered
    • Al(NO3)3 was added

       

       

  3. Consider the following three equilibria occurring simultaneously in solution.

    1.        Ca2+(aq) + CO32- (aq)  CaCO3 (s)
    2.        HCO3 –(aq)  H+(aq) + CO32- (aq)
    3.        HCO3 –(aq) + H2O(l)  H2CO3 (aq) + –OH (aq)

    If NaOH is added to the solution, will the amount of CaCO3 (s) precipitate increase, decrease or stay the same.

    4.  

     

  4. Consider the following reaction

    4CuO (s)  2 Cu2O (s) + O2 (g)

    At 1024 oC, the pressure of oxygen gas from the decomposition of copper(II) oxide is 0.49 atm.
    • Calculate Kp for this reaction at 1024 oC?
    • Calculate the fraction of CuO that will decompose if 0.16 moles of CuO is placed in a 2.0 L flask at 1024 oC.

       

       

  5. Calculate the solubility of each of the following compounds. 
    • Ag3PO4, Ksp = 1.8 x 10-18
    • CaCO3, Ksp = 8.7 x 10-9
    • Hg2Cl2, Ksp = 1.1 x 10-18

       

       

  6. For each of the following pairs of solids, determine which solid has the smallest molar solubility.
    • CaF2 (s), Ksp = 4.0 x 10-11 or BaF2 (s), Ksp = 2.4 x 10-5
    • Ca3(PO4)2  (s), Ksp = 1.3 x 10-32 or FePO4 (s), Ksp = 1.0 x 10-22

       

       

  7. The Ksp for silver sulfate is 1.2 x 10-5.  Calculate the solubility of silver sulfate in each of the following.
    • Water
    • 0.10 M AgNO3
    • 0.20M K2SO4

     

     

  8. For the following reaction:

    2NCl3 (g)  N2 (g) + 3 Cl2 (g)

    The equilibrium pressures are P (NCl3) = 0.100 atm, P (N2) = 2.30 atm, P (Cl2) = 0.0560atm.  Determine Kp for this reaction.
     

     

     

  9. The following reaction has an equilibrium constant, K = 1.8x10-7.

    CH4 (g) +  H2O (g)  CO (g)  +  3 H2 (g)

    If an initial mixture contains 1.40 M CH4, 2.30 M H2O, 1.60 M CO, and no H2 what will be the H2 concentration be when equilibrium is achieved?

     

     

  10. For the following reaction Kp = 2.4x103:

    2 NO (g)  N2 (g) +  O2 (g)

    If a 2 liter flask contains 0.024 atm NO, 2.0 atm N2, and 2.6 atm O2 how will the reaction shift?

     

     

  11. Consider the reaction of hemoglobin (Hb0 with oxygen gas and the reaction of hemoglobin and carbon monoxide:

    Hb (aq)  +  O2 (aq)  HbO2 (aq)                   K = 1.8
    Hb (aq)  +  CO (aq)  HbCO (aq)                  K = 306

    Use these reactions to determine the equilibrium constant for the following reaction, where carbon monoxide replaces oxygen in oxygenated hemoglobin:

    HbO2 (aq) +  CO (aq)  HbCO (aq)  +  O2 (aq)

     

     

  12. The reaction used in the Haber process is exothermic with the following chemical equation:

    N2 (g) +  3 H2 (g)  2 NH3 (g)
    • What will happen if an equilibrium mixture is decreased in volume (i.e., higher pressure)?
    • The temperature is increased?
    • The total pressure is increased by adding an inert gas?
    • Ammonia (NH3) is added?

       

       

  13. For the following reaction, Kp = 3.9x10-2 at 1000 K:

    CaCO3 (s)  CaO (s)  +  CO2 (g)

    A 1.25 g sample of CaCO3 (s) is introduced into a sealed container of 0.927 L volume.  It is then heated to 1000 K until equilibrium is reached. 
    • Calculate the mass of CaO (s) that is present at equilibirium.  The molar mass (MW) of CaO is 56.1 g/mol.
    • What is ∆n for the relationship:  Kp = K (RT)∆n?

       

       

  14. At a particular temperature, 12.0 mol of SO3 is placed into a 3.0 L rigid container, and dissociates according to the reaction:

    2 SO3 (g)  2 SO2 (g)  +  O2 (g)

    When equilibrium is reached, 3.0 mol of SO2 is present.  Calculate K for this reaction.

     

     

  15. Which of the following is an example of a homogeneous equilibrium?
    •  NH4NO3(s)  N2O(g) + 2 H2O(g)
    • H2(g) + I2(s)  2 HI(g)
    • CaCl2 (s) + 2 H2O(g)  CaCl2 • 2 H2O(s)
    • 2 N2O(g) + N2H4(g)  3 N2(g) + 2 H2O(g)
    • none of these

       

       

  16. Considering the following reaction

    N2O4(g)  2NO2(g)

    At –75°C, Kfor the reaction is 4.66 x 10-8. We introduce 0.036 mol of N2O4 into a 2.1-L vessel at –75°C and let equilibrium be established. What will the total pressure in the system at equilibrium will be?

     

     

  17. Considering the reaction:

    2 A(g)  2 B(g) + C(g).

    At a particular temperature  K = 1.6 x 104. If you mixed 5.0 mol B, 0.10 mol C, and 0.0010 mol A in a 1.00-L container, in which direction would the reaction initially proceed?

     

     

  18. At 25oC, Kp = 2.9 x 10-3 for the reaction

    NH4OCONH2 (s)­  2NH3 (g) + CO2 (g)

    In an experiment carried out at 25oC, a certain amount of  NH4OCONH2 is placed  in an evacuated rigid container and allowed to come to equilibrium.  Calculate the total pressure in the container at equilibrium.

     

     

  19. Given the reaction A(g) + B(g)  C(g) + D(g).  You have the gases A, B, C and D at equilibrium.  Upon adding gas A, the value of K
    • Increases because when A is added, more products are made, increasing the ratio of product to reactant.
    • Decreases because A is a reactant, so the ratio of product to reactant decreases.
    • Does not change because A does not figure in the ratio of product to reactant.
    • Does not change as long as the temperature is constant.
    • Depends on whether the reaction is exothermic or endothermic.

       

       

  20. Consider the following exothermic reaction:

    A(g) + D(s)  2B(g) + C(g)                   K = 1.6 x 104

    Determine how the following:
    • Addition of chemical B to an equilibrium mixture of the above will
      • Cause an increase in [A]
      • Cause an increase in [C]
      • Have no effect
    • Raising the pressure by lowering the volume of the container will
      • Cause an increase in [A]
      • Cause an increase in [B]
      • Have no effect.
    • Addition of chemical D to an equilibrium mixture of the above will
      • Cause a decrease in [A]
      • Cause a decrease in [B]
      • Have no effect
    • Lowering the temperature would cause an
      • Increase in [C]
      • Decrease in [B]
      • Decrease in [A]
      • More than one of the above is correct.

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