AP Chemistry                                                                                       Unit 13

Chapter 13                                                                                           Equilibrium

Daily

 

  1. Which of the following changes will change the position equilibrium?

a. allow more time to pass               b. remove some products          c. add a catalyst

d. all of these

 

  1. Calculate K (Keq=Kf/Kr) from the following information: Kf = 1.00x102 , Kr = 1.60x10-2

a. 6.25 x 103          b. 1.60             c. 4.00 x 10-5                d. 1.00 x 102

 

  1. At equilibrium, (PSCl3) = 1.00 M, (PCl3) 7.8 x 10-4 M, While K = 1.3 x 10-29. Calculate [S8] given 8PSCl3(g) D 8PCl3(g) +S8(g)

a. 1.00 M               b. 1.6 x 10-26                c. 9.5 x 10-5 M             d. 94.88 M

 

  1. For the following reaction, what must the MOLE ratio [NH3]2 / [N2][H2]3 be in a 32.5 L container if K = 6.09 x 105

N2(g) + 3 H2 (g)  ↔  2 NH3 (g)

a. 2.02 x 104          b. 1.74 x 10-3               c. 5.34 x 10-5                d. 577

 

  1. Calculate Kp at 160˚C for the following reaction:

4NO2(g) + 6H2O(g)  ↔  4NH3(g) + 5O2(g)           Kc= 0.455

a. 0.0128               b. 16.16           c. 5.97             d. 2.20

 

  1. A 0.250 L closed vessel at 487˚C contains 0.500 g of PCl5, 19.55 g of PCl3, and 10.1 g of Cl2 at equilibrium. Calculate kp based on the following equation:

PCl5(g) ↔ PCl3(g) + Cl2

a. 781        b.0.0292          c. 33.65           d. 2.10 x 103

 

  1. What is the correct equilibrium expression for the following reaction:

HCl(aq) + H2O(l) ↔ H3O+(aq) + Cl-(aq)

a. [H3O]+ [Cl]-                    b. [H3O]+ [Cl]-             c. [H2O] [HCl]             d.    [Cl]-         

-------------------              -------------------        ------------------                     ----------------

      [HCl]                              [H2O] [HCl]                      [H3O]+                   [HCl] [H2O]

 

  1. 0.125 moles of oxygen gas is added to carbon in a 0.250 L container.  The mixture equilibrates at 500 K. Calculate the equilibrium concentration of carbon monoxide, knowing that K = 0.086 at 500 K

C(s) + O2(g) ↔ 2CO(g)

a. 0.19                   b. 0.100                       c. 1.00                         d. 0.041

 

  1. 3 moles of each of the reactants and products for the following reaction are placed in a 2.00 L chamber. Predict the direction of the reaction knowing that K = 33.3

PCl5(g) ↔ PCl3(g) + Cl2(g)

a. The reaction will proceed to the right                           c. The reaction is at equilibrium

b. The reaction will proceed to the left                             d. The direction is unpredictable

 

10. Calculate the equilibrium pressure of nitrogen dioxide, when the equilibrium pressures of the nitric oxide and oxygen are 0.0100 and 0.500 atm, respectively. 

Kp = 1.00 x 104 at 200 K

2NO + O2(g) ↔ 2NO2(g)

a. 22.4 atm                   b. 0.707 atm                 c. 500 atm                    d. 3.98 atm

 

11.For the following reaction, calculate the concentration of C(aq) at equilibrium, when 0.135 M of B solution is allowed to react with A.

                                                K = 1.5 X 10-10

A(l) + B(aq) ↔ C(aq) + D(aq)

a. 0.01353 M               b. 4.5 x 10-6 M             c. 0.203 x 10-10 M                    d. 2.03 M

 

12. Which of the following changes will not affect the equilibrium position of the following equation?

A(g) + 4B(s) ↔ 2C(g) + D(g) + E(s)

a. Removal of A           b. Increase in pressure              c. Addition of E       d. Addition of C

 

13. What would you change to increase the yield of the following reaction?

A(g) + 4B(s) ↔ 2C(g) + D(g) + E(s)                ΔH = -258 kJ

a. Add B          b. Decrease temperature           c. Increase temperature d. Remove E

 

14. Write the equilibrium expression for each of the following reactions.

  1. 2H2(g) + O2(g) ↔ 2H2O(g)
  2. Cl2(g) + 2Fe2+(aq) ↔ 2Fe3+(aq) + 2Cl-(aq)
  3. Cu2+(aq) + 4NH3(aq) ↔ Cu(NH3)42+(aq)

 

15. Write the equilibrium expression for each of the following conditions.

  1. 2H2S(g) ↔ 2H2(g) + S2(g)
  2. 4NO2(g) + 6H2O(g) ↔ 4NH3(g) + 7O2(g)
  3. 2NH3(g) + 4H2O(g) ↔ 2NO2(g) + 7H2(g)
  4. PCl5(g) ↔ PCl3(g) + Cl2(g)

 

16. Calculate the equilibrium constant, Kp, at 25˚C for the reaction:

2NO(g) + O2 ↔ 2NO2(g)

If the equilibrium partial pressures are NO2 = 0.55 atm, NO = 6.5 x 10-5 atm,

O2 = 4.5 x 10-5 atm.

 

17. Calculate the value of K for the reaction: 2NO(g) + Cl2(g) ↔ 2NOCl(g) if the equilibrium concentrations are:

[NOCl] = 4.2 x 10-2 mol/L,      [NO] = 6.7 x 10-1 mol/L,          [Cl2] = 2.9 x 10-3 mol/L

 

18. Write the equilibrium expression for each of the following reactions:

  1. N2(g) + 3H2(g) ↔ 2NH3(g)
  2. I2(s) + Cl2(g) ↔ 2ICl(g)
  3. 2B(s)3F2(g) ↔ 2BF3(g)

 

19. For which of the following cases does the reaction go farthest to completion: K = 1,  K = 1010, K = 10-10?

 

20. For the system:

2HI(g) ↔ H2(g) + I2(g)

      the specific equilibrium constant of the forward reaction is 0.018 at 490˚C. Calculate the specific equilibrium constant for the backwards reaction.

 

21. Derive an expression that relates K to Kp, and calculate the value of K at 25˚C, for the reaction given in problem #16.

 

22. For the following process at 700˚C, what is the partial pressure of each gas at equilibrium if the total pressure is 0.750 atm?

C(s) + CO2(g) ↔ 2CO(g)                    Kp = 1.50

 

23. Given the initial partial pressures of p(PCl5) = 0.0500 atm, p(PCl3) = 0.150 atm, and p(Cl2) = 0.250 atm at 250˚C for the following reaction, what must each equilibrium parial pressure be?

PCl5(g) ↔ PCl3(g) + Cl2(g)                  Kp = 2.15

 

24.The reaction of methane with water is given in the following reaction:

CH4(g) + H2O(l) ↔ CO(l) + 3H2(g)          K = 5.67

Predict the direction that the system will shift in order to reach equilibrium given the following initial values of Q:

  1. Q = 11.85
  2. Q = 3.8 x 10-4
  3. Q = 5.67

 

25. Kp = 0.133 atm at a particular temperature for the reaction:

N2O4(g) ↔ 2NO2(g)

Calculate the reaction quotient, Q, if pN2O4 = 0.048 atm and pNO2 = 0.056 atm

 

26. The reaction

2NO(g) ↔ N2(g) + O2(g)

has a value of K = 2.4 x 103 at 2000 K. If 0.61 g of NO are put in a previously empty 3.00 L vessel, calculate the equilibrium concentrations of NO, N2, and O2.

 

27. Using the same reaction at 2000 K as in problem #26, calculate the equilibrium concentrations of NO, N2, and O2 if the initial concentrations of each species are: [NO] = 0 M, [N2] = 0.850 M, [O2] = 0.560.

 

28. Hypobromous acid, HOBr, dissociates in water according to the following reaction:

HOBr(aq) ↔ OBr-(aq) + H+(aq)          K = 2.06 x 10-9at 25˚C

Calculate [H+] of a solution originally 1.25 M in HOBr.

 

29. Ammonia undergoes hydrolysis according to the following reaction:

NH3(aq) + H2O ↔ NH4+(aq) + OH-(aq)          K = 1.8 x 10-5 at 25˚C

Calculate [NH3], [NH4+], and [OH-] in a solution originally 0.200 M in NH3.

 

30. Given the following reaction at 25˚C:

2SO2Cl(g) ↔ 2SO2(g) + Cl2(g)

Calculate the equilibrium constant if the equilibrium concentrations are [SO2Cl] = 0.037 M, [SO2] = 0.591 M, and [Cl2] = 1.24 M.

 

31.The equilibrium constant for the reaction:

SbCl3(g) + Cl2(g) ↔ SbCl5(g)

at 448˚C is 40. What are the equilibrium concentrations SbCl3, Cl2, and SbCl5 if [Cl2]o and [SbCl3]0 = 0.620 M and [SbCl5]o = 0.180 M?

 

32.The following chemical process is at equilibrium:

2H2(g) + O2(g) ↔ 2H2O(g)

How would the process respond if the pressure were increased at a constant temperature?

 

33.Given the following reaction at equilibrium:

Cl2(g) + 3F2(g) ↔ 2CIF3(g)

  1. Predict the effect if the pressure were reduced at a constant temperature.
  2. Predict the effect if the volume were reduced by increasing the pressure and a constant temperature.

 

34.Using the following equation, what is the effect on the equilibrium when partial pressure of ammonia is increased?

NH4Cl(s) ↔ NH3(g) + HCl(g)

 

35. In the reaction below, list ways to maximize ammonia recovery

 

                        Energy + 3H2(g) + N2 (g) ↔ 2NH3(g)