Chapter 14 2 41 Consider The Following Equilibria 2so3g 2so2g

Chapter 14 – Chemical Equilibrium

41. Consider the following equilibria:

2SO3(g) 2SO2(g) + O2(g) Kc = 2.3  10–7

2NO3(g) 2NO2(g) + O2(g) Kc = 1.4  10–3

Calculate the equilibrium constant for the reaction

SO2(g) + NO3(g) SO3(g) + NO2(g)

42. At 700 K, the reaction 2SO2(g) + O2(g) 2SO3(g) has the equilibrium constant Kc = 4.3

 106 , and the following concentrations are present: [SO2] = 0.10 M; [SO3] = 10. M; [O2] =

0.10 M. Which of the following is true based on the above?

Chapter 14 – Chemical Equilibrium

43. At 700 K, the reaction 2SO2(g) + O2(g) 2SO3(g) has the equilibrium constant Kc = 4.3

 106, and the following concentrations are present: [SO2] = 0.010 M; [SO3] = 10. M; [O2] =

0.010 M. Which of the following is true based on the above?

44. For the reaction H2(g) + I2(g) 2HI(g), Kc = 50.2 at 445ºC. If [H2] = [I2] = [HI] = 1.75 

10–3 M at 445ºC, which of the following is true based on the above?

Chapter 14 – Chemical Equilibrium

45. For the reaction PCl3(g) + Cl2(g) PCl5(g) at a particular temperature, Kc = 24.3.

Suppose a system at that temperature is prepared with [PCl3] = 0.10 M, [Cl2] = 0.15 M, and

[PCl5] = 0.60 M. Which of the following is true based on the above?

46.

For the following reaction at equilibrium, which gives a change that will shift the position of equilibrium to favor formation

of more products?

2NOBr(g) 2NO(g) + Br2(g), Hºrxn = 30 kJ/mol

Chapter 14 – Chemical Equilibrium

47.

For the following reaction at equilibrium, which change will cause the equilibrium to shift to the left?

2NOBr(g) 2NO(g) + Br2(g), Hºrxn = 30 kJ/mol

48.

For the following reaction at equilibrium in a reaction vessel, which change will cause the Br2 concentration to decrease?

2NOBr(g) 2NO(g) + Br2(g), Hºrxn= 30 kJ/mol

Chapter 14 – Chemical Equilibrium

49.

For the following reaction at equilibrium in a reaction vessel, which one of these changes would cause the Br2 concentration

to increase?

2NOBr(g) 2NO(g) + Br2(g), Hºrxn= 30 kJ/mol

50.

For the equilibrium reaction 2SO2(g) + O2(g) 2SO3(g), Hºrxn = –198 kJ/mol. Which one of these factors would cause the

equilibrium constant to increase?

Chapter 14 – Chemical Equilibrium

51. The reaction 2SO3(g) 2SO2(g) + O2(g) is endothermic. If the temperature is increased,

52.

For the reaction at equilibrium 2SO3 2SO2 + O2 (Hºrxn= 198 kJ/mol), increasing the reaction temperature would:

Chapter 14 – Chemical Equilibrium

53. Concerning the following reaction at equilibrium:

3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g), increasing the volume of the container would:

54. Concerning the following reaction at equilibrium:

3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g), increasing the concentration of the Fe(s) would:

Chapter 14 – Chemical Equilibrium

55. For the reaction at equilibrium: 3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g), removing some

of the product, Fe3O4(s), would:

56. For the reaction at equilibrium: CO(g) + H2O(g) CO2(g) + H2(g), increasing the

volume of the container would:

Chapter 14 – Chemical Equilibrium

57. Which of these situations will result if some CH4(g) is removed from the reaction

CO(g) + 3H2(g) CH4(g) + H2O(g) at equilibrium?

58.

The common allotropes of carbon (graphite and diamond) equilibrate as follows: C(gr) C(dia) with equilibrium constant

K = 0.32. The molar volumes of graphite and diamond are, respectively, 5.30 cm3/mol and 3.42 cm3/mol; Hf of diamond is

1.90 kJ/mol. This data suggests that the formation of diamond is favored at

Chapter 14 – Chemical Equilibrium

59. In which of these gas-phase equilibria is the yield of products increased by increasing the

total pressure on the reaction mixture?

60.

Consider this gas phase equilibrium system:

PCl5(g) PCl3(g) + Cl2(g) Hºrxn = +87.8 kJ/mol.

Which of these statements is false?

Chapter 14 – Chemical Equilibrium

61.

Consider this reaction at equilibrium:

2SO2(g) + O2(g) 2SO3(g), Hºrxn = –198 kJ/mol

If the volume of the system is compressed at constant temperature, what change will occur in the position of the equilibrium?

62. Consider this reaction at equilibrium at a total pressure P1:

2SO2(g) + O2(g) 2SO3(g)

Suppose the volume of this system is compressed to one-half its initial volume and then

equilibrium is reestablished. The new equilibrium total pressure will be

Chapter 14 – Chemical Equilibrium

63. For the reaction 2NOCl(g) 2NO(g) + Cl2(g), Kc = 8.0 at a certain temperature. What

concentration of NOCl must be put into an empty 4.00 L reaction vessel in order that the

equilibrium concentration of NOCl be 1.00 M?

64.

The equilibrium constants for the chemical reaction

N2(g) + O2(g) 2NO(g) are KP = 1.1  10–3 and 3.6  10–3 at 2,200 K and 2,500 K, respectively.

Which one of these statements is true?

Chapter 14 – Chemical Equilibrium

65.

When the substances in the equation below are at equilibrium, at pressure P and temperature T, the equilibrium can be shifted

to favor the products by

CuO(s) + H2(g) H2O(g) + Cu(s) Hºrxn = –2.0 kJ/mol

66. 50.0 g of N2O4 is introduced into an evacuated 2.00 L vessel and allowed to come to

equilibrium with its decomposition product, N2O4(g) 2NO2(g). For this reaction Kc =

0.133. Once the system has reached equilibrium, 5.00 g of NO2 is injected into the vessel, and

the system is allowed to equilibrate once again. Calculate the mass of NO2 in the final

equilibrium mixture.

Chapter 14 – Chemical Equilibrium

67. 50.0 g of N2O4 is introduced into an evacuated 2.00 L vessel and allowed to come to

equilibrium with its decomposition product, N2O4(g) 2NO2(g). For this reaction Kc =

0.133. Once the system has reached equilibrium, 5.00 g of NO2 is injected into the vessel, and

the system is allowed to equilibrate once again. Calculate the mass of N2O4 in the final

equilibrium mixture.

68. 75.0 g of PCl5(g) is introduced into an evacuated 3.00 L vessel and allowed to reach

equilibrium at 250ºC.

PCl5(g) PCl3(g) + Cl2(g)

If Kp = 1.80 for this reaction, what is the total pressure inside the vessel at equilibrium?

Chapter 14 – Chemical Equilibrium

69. 75.0 g of PCl5(g) is introduced into a 3.00 L vessel containing 10.0 g of Cl2(g), and the

system is allowed to reach equilibrium at 250ºC.

PCl5(g) PCl3(g) + Cl2(g)

If Kp = 1.80 for this reaction, what is the total pressure inside the vessel at equilibrium?

70. 25.0 g of HI(g) is injected into a 4.00 L reaction vessel that contains 20.0 g of I2(g). When

the system comes to equilibrium at 400ºC, what will be the total pressure inside the reaction

vessel?

2HI(g) H2(g) + I2(g), Kc = 0.0156 at 400ºC

Chapter 14 – Chemical Equilibrium

71. Solid ammonium hydrogen sulfide is introduced into a 2.00-L flask, and the flask is

sealed. If this solid decomposes according to the equation below

NH4HS(s) NH3(g) + H2S(g), Kp = 0.108 at 25C,

what is the minimum mass of ammonium hydrogen sulfide that must be present in the flask

initially if equilibrium is to be established at 25C?

72. When the reaction 2H2S(g) 2H2(g) + S2(g) is carried out at 1065C, Kp = 0.012.

Starting with pure H2S at 1065, what must the initial pressure of H2S be if the equilibrated

mixture at this temperature is to contain 0.250 atm of H2(g)?

Chapter 14 – Chemical Equilibrium

73. If the reaction 2H2S(g) 2H2(g) + S2(g) is carried out at 1065C, Kp = 0.0120. Starting

from pure H2S introduced into an evacuated vessel at 1065C, what will the total pressure in

the vessel be at equilibrium if the equilibrated mixture contains 0.300 atm of H2(g)?

74. A quantity of liquid methanol, CH3OH, is introduced into a rigid 3.00-L vessel, the vessel

is sealed, and the temperature is raised to 500K. At this temperature, the methanol vaporizes

and decomposes according to the reaction

CH3OH(g) CO(g) + 2 H2(g), Kc= 6.9010–2.

If the concentration of H2 in the equilibrium mixture is 0.426M, what mass of methanol was

initially introduced into the vessel?

Chapter 14 – Chemical Equilibrium

75.

Which of the following rate laws is consistent with the following mechanism?

A(g) + B(g) AB(g) fast equilibrium (Kc1)

AB(g) + C(g) → AC(g) + B(g) slow

76.

Which of the following rate laws is consistent with the following mechanism?

A2(g) + C(g) AC(g) + A(g) fast equilibrium (Kc1)

AC(g) + B2(g) → AB2(g) + C(g) slow

Chapter 14 – Chemical Equilibrium

77. A solution was prepared such that the initial concentrations of Cu2+(aq) and CN–(aq) were

0.0120 M and 0.0400 M, respectively. These ions react according to the following chemical

equation:

Cu2+(aq) + 4CN–(aq) Cu(CN)42–(aq)

Kc = 1.0  1025

What will be the concentration of Cu2+(aq) at equilibrium?

78. A solution was prepared such that the initial concentrations of Cu2+(aq) and CN–(aq) were

0.0120 M and 0.0400 M, respectively. These ions react according to the following chemical

equation:

Cu2+(aq) + 4CN–(aq) Cd(CN)42–(aq)

Kc = 1.0  1025

What will be the concentration of CN–(aq) at equilibrium?