Quiz # 5 Answers – Equilibrium Calculations and Trial Keq

Equilibrium Quiz # 5 Calculations and Trial Keq Answers

1. Consider the following equilibrium: N_2(g) + O_2(g) ⇄ 2NO_(g) K_eq= 0.010

Initially, a 1.0 L container is filled with 0.40 mol of N₂, 0.10 mol of O₂ and 0.080 mol of NO.

As the system approaches equilibrium, the

A. [NO], [N₂] and [O₂] remain unchanged

B. [NO] increases and both [N₂] and [O₂] decrease

C. [NO] decreases and both [N₂] and [O₂] increase

D. [NO] decreases and both [N₂] and [O₂] remain unchanged

2. Consider the following equilibrium: 2O_2(g)+ N_2(g) ⇄ N₂O_4(g)

When 2.0 mol of O₂ and 3.0 mol of N₂ were placed in a 10.0 L container at 25^oC, the value of K_eq=0.90.

If the same number of moles of reactant were placed in a 5.0 L container at 25^oC, the equilibrium constant would be

A. 0.011

B. 0.45

C. 0.90

D. 1.80

3. Consider the following equilibrium system: H₂O_(g)+ CO_(g)⇄ H_2(g)+ CO_2(g)

Initially, 5.0 moles of H₂O and 4.0 moles of CO were reacted. At equilibrium, it is found

that 2.0 moles of H₂ are present. How many moles of H₂O remain in the mixture?

A. 1.0 moles

B. 2.0 moles

C. 3.0 moles

D. 4.0 moles

4. Consider the following equilibrium: PCl_5(g) ⇄ PCl_3(g)+ Cl_2(g) K_eq=33.3

Predict what will occur when 2.0 mol of PCl₅, 3.0 mol of PCl₃ and 4.0 mol of Cl₂

are placed in a 1.0 L container and allowed to establish equilibrium.

A. [PCl₅] will increase

B. [PCl₃] and [CL₂] will both increase

C. [PCl₅] and [Cl₂] will both increase

D. [PCl₅] and [PCl₃] will both decrease

5. Consider the following equilibrium: CO_(g)+ 2H_2(g)⇄ CH₃OH_(g) ∆H= -18kJ

In order to increase the value of K_eq for this reaction, you could

A. Increase [CO]

B. Increase the volume

C. Decrease [CH₃OH]

D. Decrease the temperature

6. Consider the following: SO₂Cl_2(g) ⇄ SO_2(g) + Cl_2(g)

A 1.0 L container is initially filled with 2.0 mol of SO₂Cl₂.

As the reaction proceeds towards equilibrium, the rate of the forward reaction

A. Increases and the [SO₂] increases

B. Increases and the [SO₂] Decreases

C. Decreases and the [SO₂] increases

D. Decreases and the [SO₂] decreases

7. Consider the following: 2NO_2(g) ⇄ N₂O_2(g) K_eq=1.20

A 1.0 L of flask is filled with 1.4 mol NO₂ and 2.0 mol N₂O₄.

To reach equilibrium, the reaction proceeds to the

A. Left as Trial K_eq > K_eq

B. Left as Trial K_eq < K_eq

C. Right as Trial K_eq > K_eq

D. Right as Trial K_eq< K_eq

8. Consider the following: 2C_(s) + O_2(g) ⇄ 2CO_(g)

A 1.0 L flask is initially filled with 2.00 mol C and 0.500 mol O₂.

At equilibrium, the [O₂] is 0.250 mol/L. The K_eq value is

A. 0.444

B. 1.00

C. 2.00

D. 2.25

9. Consider the following: 2H₂O_(g) ⇄ 2H_2(g)+ O_2(g)

When 0.1010 mol H₂O is placed in a 1.000 L container, equilibrium is established.

The equilibrium concentration of O₂ is 0.0010 mol/L. the equilibrium concentrations of H₂O and H₂ are

	[H₂O]	[H₂]
A	0.0990	0.0020
B	0.1000	0.0010
C	0.1005	0.0005
D	0.1010	0.0020

10. Which of the following equilibrium systems most favors the products?

A. Cl_2(g)⇄2Cl_(g) Keq=6.4 x 10^-39

B. Cl_2(g)+ 2NO_(g) ⇄ 2NOCl_(g) Keq=3.7 x 10⁸

C. Cl_2(g)+ 2NO_2(g) ⇄ 2NO₂Cl_(g) Keq=1.8

D. 2HCl_(g) ⇄ H_2(g)+ Cl_2(g) Keq=2.0 x 10^-3

11. Consider the following equilibrium: H₂O_(g) + Cl₂O_(g) ⇄ 2HOCl_(g) K_eq= 9.0 x 10^-2

A 1.0 L flask contains a mixture of 1.8 x 10^-1 mol H₂O. 4.0 x 10^-4 mol Cl₂O, and 8.0 x 10^-2 mol HOCl .

To establish equilibrium, the system will proceed to the

A. Left as Trial K_eq > K_eq

B. Left as Trial K_eq < K_eq

C. Right as Trial K_eq > K_eq

D. Right as Trial K_eq < K_eq

12. Consider the following equilibrium: 2O_3(g) ⇄ 3O_2(g) K_eq=55

If 0.060 mol of O₃ and 0.70 mol of O₂ are introduced into a 1.0 L vessel, the

A. K_trial > K_eq and the [O₂] increases

B. K_trial < K_eq and the [O₂] increases

C. K_trial > K_eq and the [O₂] decreases

D. K_trial < K_eq and the [O₂] decreases

13. Consider the following equilibrium: CO_(g) + Cl_2(g) ⇄ COCl_2(g)

At equilibrium, a 2.0 L sample was found to contain 1.00 mol CO, 0.500 mol Cl₂

and 0.100 mol COCl₂. The K_eq value for the above system is

A. 0.40

B. 0.20

C. 2.5

D. 5.0

14 Consider the following equilibrium: 2SO_2(g)+ O_2(g)⇄ 2SO_3(g) K_eq=4.0

In an experiment, 0.40 mol SO_2(g),0.20 mol O_2(g)and 0.40 mol SO_3(g)are placed into a

1.0 liter container. Which of the following statements relates the changes in [SO₂] and [O₂]

as equilibrium becomes established?

A. The [SO₂] and [O₂] increase

B. The [SO₂] and [O₂] decrease

C. The [SO₂] and [O₂] do not change

D. The [SO₂] increases and the [O₂] decreases

15. Consider the following equilibrium system: H_2(g)+ S_(s)⇄ H₂S_(g)

In a 1.0 L container at equilibrium there are 0.050 mol H₂, 0.050 mol S and 1.0 mol H₂S.

The value of K_eq is

A. 2.5 x 10^-3

B. 5.0 x 10^-2

C. 2.0 x 10¹

D. 4.0 x 10²

16. Consider the following equilibrium and experimental data:

N₂O_4(g) ⇄ 2NO_2(g)

Initial Equilibrium

[N₂O₄] [NO₂] [N₂O₄] [NO₂]

Trial 1 0.0400 M 0.0000 M 0.0337 M 0.0125 M

Trial 2 0.0200 M 0.0600 M 0.0429 M 0.0141 M

Which of the following represents the Keq value?

A. 0.00464

B. 0.371

C. 0.742

D. 216

17. Consider the following equilibrium: Cl_2(g) + 2NO_(g) ⇌ 2NOCl_(g) Keq = 5.0

At equilibrium, [Cl₂] = 1.0 M and [NO] = 2.0 M.

What is the [NOCl] at equilibrium?

A. 0.80 M

B. 0.89 M

C. 4.5 M

D. 10 M

18. Consider the following equilibrium: Cl_2(g) + 2NO_(g) ⇌ 2NOCl_(g)

If 12.0 moles of Cl₂, 10.24 moles of NO, and 2.00 moles NOCl are placed in a

2.00 L container and the system moves to the right to get to equilibrium,

If there are 10.0 moles NOCl at equilibrium, calculate the Keq.

A. 0.996

B. 5.58

C. 1.12

D. 4.98

19. What will cause the value of Keq for an exothermic reaction to decrease?

A. increasing the pressure

B. increasing the temperature

C. decreasing the temperature

D. decreasing the surface area

20. Consider the following: H_2(g)+ I_2(g)⇌ 2HI_(g)

Initially, some HI is placed into a 1.0 L container. At equilibrium there are 0.010 mol H₂,

0.010 mol I₂ and 0.070 mol HI present. How many moles of HI were initially added to the container?

A. 0.060 mol

B. 0.070 mol

C. 0.080 mol

D. 0.090 mol

21. Consider the following equilibrium: 3NO_2(g) ⇌ N₂O_5(g) + NO_(g).

Initially, some NO₂, N₂O₅ and NO were placed in a container and allowed to reach equilibrium.

When equilibrium was established, it was found that the pressure had increased.

Which of the following explains what happened?

A. Trial Keq > Keq so the system shifted left.

B. Trial Keq < Keq so the system shifted left.

C. Trial Keq > Keq so the system shifted right.

D. Trial Keq < Keq so the system shifted right.

22. Consider the following equilibrium: 3NO_2(g) ⇌ N₂O_5(g) + NO_(g).

Initially, 8.00 moles NO₂ were placed in a 2.0 L container and allowed to reach equilibrium.

The equilibrium concentration of NO was 1.10 M. Calculate the Keq.

A. 1.7

B. 1.9

C. 3.5

D. 0.050

23. Consider the following equilibrium: 3NO_2(g) ⇌ N₂O_5(g) + NO_(g).

At a different temperature, 4.00 M NO₂ were placed in a 2.0 L container and

allowed to reach equilibrium. The equilibrium concentration of NO₂was 1.00 M. Calculate the Keq.

A. 0.11

B. 1.0

C. 3.0

D. 10.

24. Consider the reaction: 2HBr_(g) ⇌ H_2(g) + Br_2(g) Keq = 49.0

If 4.0 M HBr is initially placed into a container, what will be the equilibrium [HBr]?

A. 0.27 M

B. 3.7 M

C. 5.3 M

D. 8.8 M

25. Consider the reaction: 2HBr_(g) ⇌ H_2(g) + Br_2(g) Keq = 49.0

If 0.120 M H₂, 0.120 M Br₂ and 0.01714 M HBr are placed into a container at

44⁰ C, which of the following is true as equilibrium is approached?

A. [Br₂] decreases significantly.

B. [HBr] decreases significantly.

C. [H₂] decreases significantly.

D. [H₂] remains the same.

26. Consider the reaction: 2HBr_(g) ⇌ H_2(g) + Br_2(g) Keq = 49.0

If 1.20 M H₂, 1.20 M Br₂ and 1.00 M HBr are placed into a container at

44⁰ C, which of the following is true as equilibrium is approached?

A. [Br₂] decreases significantly.

B. [HBr] decreases significantly.

C. [H₂] decreases significantly.

D. [H₂] remains the same.

27. Which Keq is most likely to favour the formation of reactants?

A. Keq = 1.65 x 10⁴

B. Keq = 5.69 x 10^-11

C. Keq = 3.95 x 10^-11

D. Keq = 7.67 x 10⁴

28. Which Keq is most likely to favour the formation of products?

A. Keq = 1.65 x 10^-4

B. Keq = 5.69 x 10^-11

C. Keq = 3.95 x 10^-11

D. Keq = 7.67 x 10^-4

29. Consider the following equilibrium system: 2NO_(g) + Cl_2(g) ⇌ 2NOCl_(g) + 25 kJ

In which direction will the equilibrium shift and what happens to the value of Keq

when the temperature of the system is increased?

Shift Keq

A. right increases

B. right decreases

C. left increases

D. left decreases

30. Consider the following equilibrium system: 2NO_(g) + Cl_2(g) ⇌ 2NOCl_(g) + 25 kJ

In which direction will the equilibrium shift and what happens to the value of Keq when NO is added?

Shift Keq

A. right increases

B. right constant

C. left increases

D. left constant

31. Consider the following equilibrium: 2COF₂₍_g)⇌ CO_2(g) + CF_4(g)

Initially, 0.32 M CO₂ and 0.40 M CF₄ are placed in a container. At equilibrium, it is found that the [COF₂] is 0.16 M.

What is the value of Keq?

A. 0.026

B. 1.5

C. 9.3

D. 3.0

32. Consider the following equilibrium: CCl₄₍_g) ⇌ C_(s) + Cl_2(g)

Initially, 0.62 mol CCl₄ was placed in a 2.0L container.

At equilibrium, [Cl₂]= 0.060 M. Which of the following is the value of Keq?

A. 0.00039

B. 0.24

C. 0.014

D. 0.78

33. Consider the following equilibrium: 2COF₂₍_g)⇌ CO_2(g) + CF_4(g)Initially, 0.16 M CO₂ and 0.20 M CF₄ are placed in a container. At equilibrium, it is found that the [COF₂] is 0.080 M.

What is the value of Keq?

A. 0.12

B. 1.5

C. 8.0

D. 3.0