LT 12 Practice Test

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LT 12 Practice Test

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1. The value of Keq for the equilibrium H₂ (g) + I₂ (g) ↔ 2 HI (g) is 794 at 25°, What is the value of Keq for 1/2 H₂ (g) + 1/2 I₂ (g)↔HI (g)

1 point

397

0.035

1588

0.0013

Clear selection

2. The value of Keq for the equilibrium H₂ (g) + I₂ (g)↔2 HI (g) is 794 at 25°, At this temperature, what is the value of Keq for HI (g)↔1/2 H₂ (g) + 1/2 I₂ (g)

1 point

1588

397

0.035

0.0013

Clear selection

3. The value of Keq for the equilibrium H₂ (g) + I₂ (g)↔2 HI (g) is 54.0 at 427°, What is the value of Keq for HI (g)↔1/2 H₂ (g) + 1/2 I₂ (g)

1 point

7.35

0.136

2.92 × 10³

3.43 × 10⁻⁴

Clear selection

4. Consider the chemical reaction H₂ (g) + I₂ (g)↔2HI (g). At equilibrium in a particular experiment, the concentrations of H₂, I₂, and HI were 0.15M, 0.033M and 0.55M respectively. The value of Keq for this reaction is __________.

1 point

111

9.0 × 10⁻³

6.1

Clear selection

5. A reaction vessel is charged with hydrogen iodide, which partially decomposes to molecular hydrogen and iodine according to the equation 2HI (g)↔H₂(g) + I₂(g). When the system comes to equilibrium at 425°C, P HI = 0.708 atm, and P H₂ = P I₂ = 0.0960 atm. The value of Kp at this temperature is __________.

1 point

6.80 × 10⁻²

1.30 × 10⁻²

Kp cannot be calculated for this gas reaction when the volume of the reaction vessel is not given.

54.3

1.84 × 10⁻²

Clear selection

6. Acetic acid is a weak acid that dissociates into the acetate ion and a proton in aqueous solution, HC₂H₃O₂ (aq)↔C₂H₃O₂⁻ (aq) + H⁺ (aq). At equilibrium at 25°C a 0.100 M solution of acetic acid has the following concentrations: [HC₂H₃O₂] = 0.0990M, [C₂H₃O₂⁻] = 1.33x10⁻³ and [H⁺] = 1.33x10⁻³ The equilibrium constant, Keq, for the ionization of acetic acid at 25°C is __________.

1 point

5.71 × 10⁴

0.100

1.75 × 10⁻⁷

1.79 × 10⁻⁵

5.71 × 10⁶

Clear selection

7. At elevated temperatures, molecular hydrogen and molecular bromine react to partially form hydrogen bromide, H₂ (g) + Br₂ (g)↔2HBr (g). A mixture of 0.682 mol of H₂ and 0.440 mol of Br₂ is combined in a reaction vessel with a volume of 2.00 L. At equilibrium at 700 K, there are 0.566 mol of H₂ present. At equilibrium, there are __________ mol of Br₂ present in the reaction vessel.

1 point

0.000

0.440

0.566

0.232

0.324

Clear selection

8. Dinitrogen tetroxide partially decomposes according to the following equilibrium, N₂O₄ (g)↔2NO₂ (g). A 1.00-L flask is charged with 0.0400 mol of N₂O₄. At equilibrium at 373 K, 0.0055 mol of N₂O₄ remains. Keq for this reaction is __________.

1 point

2.2 × 10⁻⁴

0.22

0.022

0.87

Clear selection

9. At 22°C, Kp = 0.070 for the equilibrium, NH₄HS (s)↔NH₃ (g) + H₂S (g). A sample of solid NH₄HS is placed in a closed vessel and allowed to equilibrate. Calculate the equilibrium partial pressure (atm) of ammonia, assuming that some solid NH₄HS remains.

1 point

0.26

0.070

0.52

4.9 × 10⁻³

3.8

Clear selection

10. In the coal-gasification process, carbon monoxide is converted to carbon dioxide via the following reaction, CO (g) + H₂O (g)↔CO₂ (g) + H₂ (g). In an experiment, 0.35 mol of CO and 0.40 mol of H₂O were placed in a 1.00-L reaction vessel. At equilibrium, there were 0.19 mol of CO remaining. Keq at the temperature of the experiment is __________.

1 point

5.47

0.75

1.78

0.56

1.0

Clear selection

11. A sealed 1.0 L flask is charged with 0.500 mol of I₂ and 0.500 mol of Br₂. An equilibrium reaction ensues, I₂ (g) + Br₂ (g)↔2IBr (g). When the container contents achieve equilibrium, the flask contains 0.84 mol of IBr. The value of Keq is __________.

1 point

4.0

110

6.1

2.8

Clear selection

12. The equilibrium constant (Kp) for the interconversion of PCl₅ and PCl₃ is 0.0121 [PCl₅ (g)↔PCl₃ (g) + Cl₂ (g)]. A vessel is charged with PCl₅, giving an initial pressure of 0.123 atm. At equilibrium, the partial pressure of PCl₃ is __________ atm.

1 point

0.0782

0.0455

0.0908

0.0330

0.123

Clear selection

13. Kp = 0.0198 at 721 K for the reaction, 2HI (g)↔H₂ (g) + I₂ (g). In a particular experiment, the partial pressures of H₂ and I₂ at equilibrium are 0.710 and 0.888 atm, respectively. The partial pressure of HI is __________ atm.

1 point

7.87

1.98

5.64

0.125

0.389

Clear selection

14. At 200°C, the equilibrium constant (Kp) for the reaction 2NO (g)↔N₂(g) + O₂(g) is 2.40 × 10³. A closed vessel is charged with 36.1 atm of NO. At equilibrium, the partial pressure of O₂ is __________ atm.

1 point

294

35.7

17.9

6.00

1.50 × 10⁻²

Clear selection

15. At equilibrium, __________.

1 point

all chemical reactions have ceased

the rates of the forward and reverse reactions are equal

the rate constants of the forward and reverse reactions are equal

the value of the equilibrium constant is 1

the limiting reagent has been consumed

Clear selection

16. Which one of the following will change the value of an equilibrium constant?

1 point

changing temperature

adding other substances that do not react with any of the species involved in the equilibrium

varying the initial concentrations of reactants

varying the initial concentrations of products

changing the volume of the reaction vessel

Clear selection

17. Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide; N₂O₄ (g)↔2NO₂ (g).

1 point

Clear selection

18. The equilibrium-constant expression (Keq) depends on the __________ of the reaction.

1 point

stoichiometry

mechanism

stoichiometry and mechanism

the quantities of reactants and products initially present

temperature

Clear selection

20. Given the following reaction at equilibrium at 300.0 K: NH₄HS (s)↔NH₃ (g) + H₂S (g). If P NH₃ = P H₂S = 0.111 atm, Kp = __________.

1 point

1.23 x 10⁻²

4.99 x 10⁻⁴

1.11 x 10⁻¹

8.12 x 10⁻²

5.66 x 10⁻³

Clear selection

21. Which of the following expressions is the correct equilibrium-constant expression for the reaction (NH4)₂Se (s)↔2NH₃ (g) + H₂Se (g)?

1 point

[NH₃][H₂Se] / [(NH₄)₂Se]

[(NH₄)₂Se] / [NH₃]²[H₂Se]

1 / [(NH₄)₂Se]

[NH₃]²[H₂Se]

[NH₃]²[H₂Se] / [(NH₄)₂Se]

Clear selection

22. Which of the following expressions is the correct equilibrium-constant expression for the reaction HF (aq) + H₂O (l)↔H₃O+ (aq) + F- (aq) ?

1 point

[HF][H₂O] / [H₃O+][F-]

1 / [HF]

[H₃O+][F-] / [HF][H₂O]

[H₃O+][F-] / [HF]

[F-] / [HF]

Clear selection

23. The equilibrium constant for the gas phase reaction N₂ (g) + 3H₂ (g)↔2NH₃ (g) is Keq = 4.34 × 10⁻³ at 300°C. At equilibrium, __________.

1 point

products predominate

reactants predominate

roughly equal amounts of products and reactants are present

only products are present

only reactants are present

Clear selection

24. The equilibrium constant for the gas phase reaction 2NH₃ (g)↔N₂ (g) + 3H₂ (g) is Keq = 230 at 300°, At equilibrium, __________.

1 point

products predominate

reactants predominate

roughly equal amounts of products and reactants are present

only products are present

only reactants are present

Clear selection

25. The equilibrium constant for reaction 1 is K. The equilibrium constant for reaction 2 is __________.

(1) SO₂ (g) + (1/2) O₂ (g)↔SO₃ (g) (2) 2SO₃ (g)↔2SO₂ (g) + O₂ (g)

1 point

K²

1/2K

1/K²

-K²

Clear selection

26. The value of Keq for the following reaction is 0.25; SO₂ (g) + NO₂ (g)↔SO₃ (g) + NO (g). The value of Keq at the same temperature for the reaction below is __________.

2SO₂ (g) + 2NO₂ (g)↔ 2SO₃ (g) + 2NO (g)

1 point

0.50

0.063

0.12

0.25

Clear selection

27. The equilibrium expression for Kp for the reaction below is __________.

2O₃ (g)↔3O₂ (g)

1 point

Clear selection

28. The Keq for the equilibrium reaction 2Cl₂ (g) + 2H₂O (g)↔4HCl (g) + O₂ (g) is 7.52 × 10⁻² at 480.0°C. What is the value of Keq at this temperature for the following reaction?

Cl₂ (g) + H₂O (g)↔2HCl (g) + O₂ (g)

1 point

0.0752

5.66 × 10⁻³

0.274

0.0376

0.150

Clear selection

29. The Keq for the reaction 2Cl₂ (g) + 2H₂O (g)↔4HCl (g) + O₂ (g) is 7.52 × 10⁻² at 480.0°C. What is the value of Keq at this temperature for the following reaction?

4HCl (g) + O₂ (g)↔2Cl₂ (g) + 2H₂O (g)

1 point

0.0752

-0.0752

13.3

5.66 × 10-3

0.150

Clear selection

30. The Keq for the reaction 2Cl₂ (g) + 2H₂O (g)↔4HCl (g) + O₂ (g) is 7.52 × 10⁻² at 480.0°C. What is the value of Keq at this temperature for the following reaction?

2HCl (g) + O₂ (g)↔Cl₂ (g) + H₂O (g)

1 point

13.3

3.65

-0.0376

5.66 × 10⁻³

0.274

Clear selection

31. The Keq for the reaction SO₂ (g) + O₂ (g)↔SO₃ (g) is 0.112 at 700.0°C. What is the value of Keq at this temperature for the following reaction?

2SO₂ (g) + O₂ (g)↔2SO₃ (g)

1 point

0.224

0.335

0.0125

0.0560

0.112

Clear selection

32. The Keq for the reaction SO₂ (g) + O₂ (g)↔SO₃ (g) is 0.112 at 700.0°C. What is the value of Keq at this temperature for the following reaction?

SO₃ (g)↔SO₂ (g) + O₂ (g)

1 point

0.224

0.0125

0.112

8.93

-0.112

Clear selection

33. The Keq for the reaction SO₂ (g) + O₂ (g)↔SO₃ (g) is 0.112 at 700.0°C. What is the value of Keq at this temperature for the following reaction?

2SO₃ (g)↔2SO₂ (g) + O₂ (g)

1 point

79.7

2.99

17.86

4.46

8.93

Clear selection

34. At 1000.0 K, the equilibrium constant for the reaction 2NO (g) + Br₂ (g)↔2NOBr (g) is Kp = 0.013. Calculate Kp for the reverse reaction,

2NOBr (g)↔2NO (g) + Br₂ (g).

1 point

0.013

1.6 × 10-4

0.99

1.1

Clear selection

35. The expression for Kp for the reaction below is __________.

4CuO (s) + CH₄ (g)↔CO₂ (g) + 4Cu (s) + 2H₂O (g)

1 point

Clear selection

36. The equilibrium-constant expression for the reaction Ti (s) + 2Cl₂ (g)↔TiCl₄ (l) is given by

1 point

Clear selection

37. At 400 K, the equilibrium constant for the reaction Br₂ (g) + Cl₂ (g)↔2BrCl (g) is Kp = 7.0. A closed vessel at 400 K is charged with 1.00 atm of Br₂ (g), 1.00 atm of Cl₂ (g), and 2.00 atm of BrCl (g). Use Q to determine which of the statements below is true.

1 point

The equilibrium partial pressures of Br₂ and Cl2 and BrCl will be the same as the initial values.

The equilibrium partial pressure of Br₂ will be greater than 1.00 atm.

At equilibrium the total pressure in the vessel will be less than the initial total pressure.

The equilibrium partial pressure of BrCl (g) will be greater than 2.00 atm.

The reaction will go to completion since there are equal amounts of Br₂ and Cl2.

Clear selection

38. Which of the following statements is true?

1 point

Q does not change with temperature.

Keq does not change with temperature whereas Q is temperature dependent.

K does not depend on the concentrations or partial pressures of reaction components.

Q does not depend on the concentrations or partial pressures of reaction components.

Q is the same as Keq when a reaction is at equilibrium.

Clear selection

39. How is the reaction quotient used to determine whether a system is at equilibrium?

1 point

The reaction quotient must be satisfied for equilibrium to be achieved.

At equilibrium

the reaction quotient is undefined.

The reaction is at equilibrium when Q < Keq.

The reaction is at equilibrium when Q > Keq.

The reaction is at equilibrium when Q = Keq.

Clear selection

40. Nitrosyl bromide decomposes according to the following equation: 2NOBr (g)↔2NO (g) + Br₂ (g). A sample of NOBr (0.64 mol) was placed in a 1.00-L flask containing no NO or Br₂. At equilibrium the flask contained 0.46 mol of NOBr. How many moles of NO and Br₂, respectively, are in the flask at equilibrium?

1 point

0.18, 0.18

0.46, 0.23

0.18, 0.090

0.18, 0.360

0.46, 0.46

Clear selection

41. Of the following equilibria, only __________ will shift to the left in response to a decrease in volume.

1 point

H₂ (g) + Cl₂ (g)↔ 2 HCl (g)

2 SO₃ (g)↔2 SO₂ (g) + O₂ (g)

N₂ (g) + 3 H₂ (g)↔2 NH₃ (g)

4 Fe (s) + 3 O₂ (g)↔2 Fe₂O₃ (s)

2HI (g)↔H₂ (g) + I₂ (g)

Clear selection

42. The reaction 2SO₂ (g) + O₂ (g)↔2SO₃ (g )is exothermic. Le Chätelier's Principle predicts that __________ will result in an increase in the number of moles of SO₃ (g) in the reaction container.

1 point

increasing the pressure

decreasing the pressure

increasing the temperature

removing some oxygen

increasing the volume of the container

Clear selection

43. For the endothermic reaction CaCO₃ (s)↔CaO (s) + CO₂ (g), Le Chätelier's principle predicts that __________ will result in an increase in the number of moles of CO₂.

1 point

increasing the temperature

decreasing the temperature

increasing the pressure

removing some of the CaCO₃ (s)

none of the above

Clear selection

44. In which of the following reactions would increasing pressure at constant temperature not change the concentrations of reactants and products, based on Le Chätelier's principle?

1 point

N₂ (g) + 3H₂ (g)↔ 2NH₃ (g)

N₂O₄ (g)↔2NO₂ (g)

N₂ (g) + 2O₂ (g)↔2NO₂ (g)

2N₂ (g) + O₂ (g)↔2N₂O (g)

N₂ (g) + O₂ (g)↔2NO (g)

Clear selection

45. Consider the following reaction at equilibrium: 2NH₃ (g)↔N₂ (g) + 3H₂ (g) ΔH° = +92.4 kJ. Le Chätelier's principle predicts that adding N₂ (g) to the system at equilibrium will result in __________.

1 point

a decrease in the concentration of NH₃ (g)

a decrease in the concentration of H₂ (g)

an increase in the value of the equilibrium constant

a lower partial pressure of N₂

removal of all of the H₂ (g)

Clear selection

46. Consider the following reaction at equilibrium: 2NH₃ (g)↔N₂ (g) + 3H₂ (g). Le Chätelier's principle predicts that the moles of H₂ in the reaction container will increase with __________.

1 point

some removal of NH₃ from the reaction vessel (V and T constant)

a decrease in the total pressure (T constant)

addition of some N₂ to the reaction vessel (V and T constant)

a decrease in the total volume of the reaction vessel (T constant)

an increase in total pressure by the addition of helium gas (V and T constant)

Clear selection

47. Consider the following reaction at equilibrium: 2CO₂ (g)↔2CO (g) + O₂ (g) ΔH° = -514 kJ. Le Chätelier's principle predicts that adding O₂ (g) to the reaction container will __________.

1 point

increase the partial pressure of CO (g) at equilibrium

decrease the partial pressure of CO₂ (g) at equilibrium

increase the value of the equilibrium constant

increase the partial pressure of CO₂ (g) at equilibrium

decrease the value of the equilibrium constant

Clear selection

48. Consider the following reaction at equilibrium: 2CO₂ (g)↔2CO (g) + O₂ (g) ΔH° = -514 kJ. Le Chätelier's principle predicts that an increase in temperature will __________.

1 point

increase the partial pressure of O₂ (g)

decrease the partial pressure of CO₂ (g)

decrease the value of the equilibrium constant

increase the value of the equilibrium constant

increase the partial pressure of CO

Clear selection

49. Consider the following reaction at equilibrium: C (s) + H₂O (g)↔CO (g) + H₂ (g). Which of the following conditions will increase the partial pressure of CO?

1 point

decreasing the partial pressure of H₂O (g)

removing H₂O (g) from the system

decreasing the volume of the reaction vessel

decreasing the pressure in the reaction vessel

increasing the amount of carbon in the system

Clear selection

50. Consider the following reaction at equilibrium; 2CO₂ (g)↔2CO (g) + O₂ (g) ΔH° = -514 kJ. Le Chätelier's principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction __________.

1 point

at high temperature and high pressure

at high temperature and low pressure

at low temperature and low pressure

at low temperature and high pressure

in the presence of solid carbon

Clear selection

52. The effect of a catalyst on an equilibrium is to __________.

1 point

increase the rate of the forward reaction only

increase the equilibrium constant so that products are favored

slow the reverse reaction only

increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture

shift the equilibrium to the right

Clear selection

53. Phosphorous trichloride and phosphorous pentachloride equilibrate in the presence of molecular chlorine according to the reaction: PCl₃ (g) + Cl₂ (g) → PCl₅ (g). An equilibrium mixture at 450 K contains P PCl₃ = 0.202 atm, P Cl₂ = 0.256 atm, and P PCl₅ = 3.45 atm. What is the value of Kp at this temperature?

1 point

66.7

1.50 × 10⁻²

1.78 × 10⁻¹

2.99

7.54

Clear selection

54. Dinitrogen tetroxide partially decomposes according to the following equilibrium: N₂O₄ (g) → 2NO₂ (g). A 1.000-L flask is charged with 3.00 × 10⁻² mol of N₂O₄. At equilibrium, 2.36 × 10⁻² mol of N₂O₄ remains. Keq for this reaction is __________.

1 point

0.723

0.391

0.212

6.94 × 10⁻³

1.92 × 10⁻⁴

Clear selection

55. The Kp for the reaction CO (g) + Cl₂ (g) ↔ COCl₂ (g) is 1.49 × 10⁸ at 100.0°C. In an equilibrium mixture of the three gases, P CO = P Cl₂ = 8.60 × 10⁻⁴ atm. The partial pressure of the product, phosgene (COCl₂), is __________ atm.

1 point

1.10 × 10²

2.01 × 10¹⁴

4.96 × 10⁻¹⁵

1.28 × 10⁵

1.72 × 10¹¹

Clear selection

56. At 900.0 K, the equilibrium constant (Kp) for the reaction 2SO₂ + O₂ (g) → 2SO₃ (g)is 0.345. At equilibrium, the partial pressure of SO₂ is 35.0 atm and that of O₂ is 15.9 atm. The partial pressure of SO₃ is __________ atm.

1 point

82.0

4.21 × 10⁻³

192

6.20 × 10⁻⁴

40.2

Clear selection

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