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- 1. Multiple Choice
A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1.0 L container. Which of the following species will have the highest concentration when the system reaches equilibrium?
H2S (g)
CH4 (g)
CS2 (g)
H2 (g)
- 2. Multiple Choice
2 S(s) + 2 O2(g) ⇄ 2 SO2(g) K1 = 2 x 10105
2 SO2(g) + O2(g) ⇄ 2 SO3(g) K2 = 7 x 1024
Given the value of the equilibrium constants K1 and K2 for the reactions represented above, what is the value of the equilibrium constant, K3, for the following reaction?
2 S(s) + 3 O2(g) ⇄ 2 SO3(g) K3 = ?
1 x 10130
3 x 1080
1 x 1065
2 x 1040
7 x 1024
- 3. Multiple Choice
2 XY(g) ⇄ X2(g) + Y2(g) Kp = 230
A certain gas, XY(g), decomposes as represented by the equation above. A sample of each of the three gases is put in a previously evacuated container. The initial partial pressures of the gases are shown in the table.
The temperature of the reaction mixture is held constant. In which direction will the reaction proceed?
The reaction will form more products.
The reaction will form more reactant.
The mixture is at equilibrium, so there will be no change.
It cannot be determined unless the volume of the container is known.
- 4. Multiple Choice
2X(g) + Y(g) ⇄ 3Z(g)
The reaction mixture represented above is at equilibrium at 298 K, and the molar concentrations are [X] = 2.0 M, [Y] = 0.5 M, and [Z] = 4.0 M. What is the value of the equilibrium constant for the reaction at 298 K ?
0.50
2.0
4.0
16
32
- 5. Multiple Choice
3 O2(g) ⇄ 2O3(g) Kc = 1.8 × 10−56 at 570 K
For the system represented above, [O2] and [O3] initially are 0.150 mol/L and 2.5 mol/L respectively. Which of the following best predicts what will occur as the system approaches equilibrium at 570 K?
The amount of O3(g) will increase, because Q < Kc.
The amount of O3(g) will decrease, because Q < Kc.
The amount of O3(g) will increase, because Q > Kc.
The amount of O3(g) will decrease, because Q > Kc.
- 6. Multiple Choice
A 2.0 mol sample of CO(g) and a 2.0 mol sample of H2O(g) are introduced into a previously evacuated 100. L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?
[H2O] > [CO] and [CO2] > [H2]
[H2O] > [H2]
[CO2] > [CO]
[CO] = [H2O] = [CO2] = [H2]
- 7. Multiple Choice
CO(g) + 2 H2(g) ⇄ CH3OH(g) ΔH < 0
The synthesis of CH3OH(g) from CO(g) and H2(g) is represented by the equation above. The value
of Kc for the reaction at 483 K is 14.5.
A 1.0 mol sample of CO(g) and a 1.0 mol sample of H2(g) are pumped into a rigid, previously evacuated 2.0 L reaction vessel at 483 K. Which of the following is true at equilibrium?
[H2] = 2[CO]
[H2] < [CO]
[CO] = [CH3OH] < [H2]
[CO] = [CH3OH] = [H2]
- 8. Multiple Choice
COCl2(g) ⇄ CO(g) + Cl2(g)
COCl2(g) decomposes according to the equation above. When pure COCl2(g) is injected into a rigid, previously evacuated flask at 690 K, the pressure in the flask is initially 1.0 atm. After the reaction reaches equilibrium at 690 K, the total pressure in the flask is 1.2 atm. What is the value of Kp for the reaction at 690 K?
0.040
0.050
0.80
1.0
- 9. Multiple Choice
The equilibrium reaction between Cl2 (aq) and H2O (l) at 25 oC is represented by the chemical equation shown above. If a solution at equilibrium at 25 oC is diluter with distilled water to twice its original volume, which of the following gives the value for Q and predicts the response by the system immediately after dilution?
Q = 4 K, and the rate of the reverse reaction will be greater than the rate of the forward reaction.
Q = 4 K, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
Q = K/4, and the rate of the reverse reaction will be greater than the rate of the forward reaction.
Q = K/4, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
- 10. Multiple Choice
2 NO(g) + Cl2(g) ↔ 2 NOCl(g) K = 2000
A mixture of NO(g) and Cl2 (g) is placed in a previously evacuated container and allowed to reach equilibrium according to the chemical equation shown above. When the system reaches equilibrium, the reactants and products have the concentrations listed in the table. Which of the following is true if the volume of the container is decreased by one half?
Q = 100, and the reaction will proceed toward reactants.
Q = 100, and the reaction will proceed toward products.
Q = 1000, and the reaction will proceed toward reactants.
Q = 1000, and the reaction will proceed toward products.
- 11. Multiple Choice
Equal volumes of 0.1 M AgNO3(aq) and 2.0 M NH3(aq) are mixed and the reactions represented above occur. Which Ag species will have the highest concentration in the equilibrium system shown below, and why?
Ag+(aq) + 2 NH3 (aq) ↔ Ag(NH3)2+ (aq) Keq3 = ?
Ag+(aq), because Keq3 = 4
Ag+(aq), because Keq1 < Keq2
Ag(NH3)2+ (aq), because Keq3 = 1.6 x 107
Ag(NH3)2+ (aq), because Keq1 < Keq2
- 12. Multiple Choice
The diagram above represents the equilibrium between the two isomers of C2H2Cl2, and the table provides the data collected in an experiment to determine its equilibrium constant, Kc at 490 K. In a second experiment done at the same temperature, [Z]eq ≈ 1.0 M. Which of the following is the approximate equilibrium concentration of Y in the second experiment, and why?
[Y]eq ≈ 1.4 M because [Y]eq - [Z]eq should be the same for the same reaction.
[Y]eq ≈ 1.5 M because the ration [Z]eq / [Y]eq should remain constant when the reaction is done at the same temperature.
[Y]eq ≈ 1.6 M because the ration [Y]initial / [Y]eq should remain constant when the reaction is done at the same temperature.
[Y]eq ≈ 2.0 M because ([Y]initial - [Y]eq) = ([Z]initial - [Z]eq) should be the same for the same reaction.
- 13. Multiple Choice
2 A(g) + B(g) ↔ 2 C(g)
A(g) and B(g) react to form C(g), according to the balanced equation above. In an experiment, a previously evacuated rigid vessel is charged with A(g), B(g), and C(g), each with a concentration of 0.0100 M. The table shows the concentrations of the gases at equilibrium at a particular temperature.
If the experiment is repeated at a higher temperature at which Kc is larger, which of the following best describes the effect of the temperature change on the concentrations of the gases at equilibrium?
[A]eq, [B]eq, and [C]eq will all increase because Kc increased.
[A]eq, and [B]eq will remain constant, but [C]eq will increase because Kc increased.
There will be a decrease in [A]eq that will be two times the decrease in [B]eq because A and B react in a 2-to-1 ratio.
There will be an increase in [A]eq that will be two times the increase in [B]eq because A and B react in a 2-to-1 ratio.
- 14. Multiple Choice
The system represented by the equation above is allowed to establish equilibrium. The initial pressures of the substances are given in the table. Which of the following explains what the system will do as it approaches equilibrium?
Q > Kp and equilibrium will be approached by producing NOBr because the forward reaction is faster than the reverse reaction.
Q < Kp and equilibrium will be approached by producing NOBr because the forward reaction is faster than the reverse reaction.
Q < Kp and equilibrium will be approached by consuming NOBr because the reverse reaction is faster than the forward reaction.
Q > Kp and equilibrium will be approached by consuming NOBr because the reverse reaction is faster than the forward reaction.
- 15. Multiple Choice
The decomposition of HI(g) at 298 K is represented by the equilibrium equation above. When 100. torr of HI(g) is added to a previously evacuated, rigid container and allowed to reach equilibrium, the partial pressure of I2(g) is approximately 3.7 torr. If the initial pressure of HI(g) is increased to 200. torr and the process is repeated at the same temperature, which of the following correctly predicts the equilibrium partial pressure of I2(g), and why?
PI2 ≈ 14 torr, because it is directly proportional to the square of the initial pressure of HI.
PI2 ≈ 0.073 torr, because it is inversely proportional to the square of the initial pressure of HI.
PI2 ≈ 7.4 torr, because it is directly proportional to the initial pressure of HI.
PI2 ≈ 1.9 torr, because it is inversely proportional to the initial pressure of HI.
- 16. Multiple Choice
H2(g) + Br2(g) ⇄ 2HBr(g)
At a certain temperature, the value of the equilibrium constant,K, for the reaction represented above is 2.0 x 105. What is the value of K for the reverse reaction at the same temperature?
-2.0 x 10-5
5.0 x 10-6
2.0 x 10-5
5.0 x 10-5
5.0 x 10-4
- 17. Multiple Choice
H2(g) + I2(g) ⇄ 2 HI(g)
At 450oC, 2.0 moles each of H2(g), I2(g), and HI(g) are combined in a 1.0 L rigid container. The value of Kc at 450oC is 50. Which of the following will occur as the system moves toward equilibrium?
More H2(g) and I2(g) will form.
More HI(g) will form.
The total pressure will decrease.
No net reaction will occur, because the number of molecules is the same on both sides of the equation.
- 18. Multiple Choice
A mixture of NO2(g) and N2O4(g) is placed in a glass tube and allowed to reach equilibrium at 70°C, as represented above.
If PN2O4 is 1.33 atm when the system is at equilibrium at 70 oC, what is PNO2?
0.44 atm
2.0 atm
2.3 atm
4.0 atm
- 19. Multiple Choice
The table above lists some equilibrium systems and their equilibrium constants. Which of the following identifies the correct mathematical relationship that uses the information to calculate K5?
- 20. Multiple Choice
N2O5(g) ⇄ 2 NO2(g) + 1⁄2 O2(g)
The equilibrium constant for the gas phase reaction above is 95 at 25°C. What is the value of the equilibrium constant for the following reaction at 25°C?
O2(g) + 4 NO2(g) ⇄ 2 N2O5(g)
(95)2
95
(95)1/2
1/95
1/(95)2
- 21. Multiple Choice
Based on the equilibrium constants given above, which of the following gives the correct expression for the equilibrium constant for reaction 3?
- 22. Multiple Choice
PCl3(g) + Cl2(g) ⇄ PCl5(g) Kc = 6.5
At a certain point in time, a 1.00 L rigid reaction vessel contains 1.5 mol of PCl3(g), 1.0 mol of Cl2(g), and 2.5 mol of PCl5(g). Which of the following describes how the measured pressure in the reaction vessel will change and why it will change that way as the reaction system approaches equilibrium at constant temperature?
The pressure will increase because Q < Kc.
The pressure will increase because Q > Kc.
The pressure will decrease because Q < Kc.
The pressure will decrease because Q > Kc.
- 23. Multiple Choice
Based on the information above, which of the following expressions represents the equilibrium constant, K, for the reaction represented by the equation below?
La3+ + CO32− ⇄ LaCO3+
- 24. Multiple Choice
X(g) + 2 Q(g) ⇄ R(g) + Z(g) Kc = 1.3 × 105 at 50°C
A 1.0 mol sample of X(g) and a 1.0 mol sample of Q(g) are introduced into an evacuated, rigid 10.0 L container and allowed to reach equilibrium at 50°C according to the equation above. At equilibrium, which of the following is true about the concentrations of the gases?
[R] = 1/2[Q]
[Q] = 1/2[X]
[R] = [Z] > [Q]
[x] = [Q] = [R] = [Z]
- 25. Multiple Choice
X(g) + Y(g) ⇄ 2Z(g)
When 4.00 mol each of X(g) and Y(g) are placed in a 1.00 L vessel and allowed to react at constant temperature according to the equation above, 6.00 mol of Z(g) is produced. What is the value of the equilibrium constant, Kc?
3
6
8
16
36
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