Answer at the bottom of the page

 

15.1 Multiple-Choice Questions

1) At equilibrium, __________.

A) all chemical reactions have ceased

B) the rates of the forward and reverse reactions are equal

C) the rate constants of the forward and reverse reactions are equal

D) the value of the equilibrium constant is 1

E) the limiting reagent has been consumed

2) What role did Karl Bosch play in development of the Haber-Bosch process?

A) He discovered the reaction conditions necessary for formation of ammonia.

B) He originally isolated ammonia from camel dung and found a method for purifying it.

C) Haber was working in his lab with his instructor at the time he worked out the process.

D) He developed the equipment necessary for industrial production of ammonia.

E) He was the German industrialist who financed the research done by Haber.

3) In what year was Fritz Haber awarded the Nobel Prize in chemistry for his development of a process for synthesizing ammonia directly from nitrogen and hydrogen?

A) 1954

B) 1933

C) 1918

D) 1900

E) 1912

4) Which one of the following is true concerning the Haber process?

A) It is a process used for shifting equilibrium positions to the right for more economical chemical synthesis of a variety of substances.

B) It is a process used for the synthesis of ammonia.

C) It is another way of stating Le Châtelier’s principle.

D) It is an industrial synthesis of sodium chloride that was discovered by Karl Haber.

E) It is a process for the synthesis of elemental chlorine.

5) Which one of the following will change the value of an equilibrium constant?

A) changing temperature

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

C) varying the initial concentrations of reactants

D) varying the initial concentrations of products

E) changing the volume of the reaction vessel

6) Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide?

N2O4 (g) 2NO2 (g)

A)

B)

C)

D) [NO2][N2O4]

E) [NO2]2[N2O4]

7) Which of the following expressions is the correct equilibrium-constant expression for the following reaction?

CO2 (g) + 2H2 (g) CH3OH (g)

A)

B)

C)

D)

E)

8) The equilibrium-constant expression depends on the __________ of the reaction.

A) stoichiometry

B) mechanism

C) stoichiometry and mechanism

D) the quantities of reactants and products initially present

E) temperature

9) 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)

A) K2

B) 2K

C) 1/2K

D) 1/K2

E) -K2

10) 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)

A) 0.50

B) 0.063

C) 0.12

D) 0.25

E) 16

11) The equilibrium expression for Kp for the reaction below is __________.

2O3 (g) 3O2 (g)

A)

B)

C)

D)

E)

12) The equilibrium expression for Kp for the reaction below is __________.

N2 (g) + O2 (g) 2NO (g)

A)

B)

C)

D)

E) none of the above

13) The Keq for the equilibrium below is 7.52 × 10-2 at 480.0°C.

2Cl2 (g) + 2H2O (g) 4HCl (g) + O2 (g)

What is the value of Keq at this temperature for the following reaction?

4HCl (g) + O2 (g) 2Cl2 (g) + 2H2O (g)

A) 0.0752

B) -0.0752

C) 13.3

D) 5.66 × 10-3

E) 0.150

14) The Keq for the equilibrium below is 5.4 × 1013 at 480.0°C.

2NO (g) + O2 (g) 2NO2 (g)

What is the value of Keq at this temperature for the following reaction?

4NO (g) + 2O2 (g) 4NO2 (g)

A) 5.4 × 1013

B) 5.4 × 10-13

C) 1.9 × 1012

D) 1.9 × 10-12

E) 2.9 × 1027

15) The Keq for the equilibrium below is 7.52 × 10-2 at 480.0°C.

2Cl2 (g) + 2H2O (g) 4HCl (g) + O2 (g)

What is the value of Keq at this temperature for the following reaction?

2HCl (g) + O2 (g) Cl2 (g) + H2O (g)

A) 13.3

B) 3.65

C) -0.0376

D) 5.66 × 10-3

E) 0.274

16) The Keq for the equilibrium below is 5.4 × 1013 at 480.0°C.

2NO (g) + O2 (g) 2NO2 (g)

What is the value of Keq at this temperature for the following reaction?

NO2 (g) NO (g) + 1/2 O2 (g)

A) 5.4 × 10-13

B) 5.4 × 1013

C) 1.4 × 10-7

D) 5.66 × 10-3

E) none of the above

17) The Keq for the equilibrium below is 0.112 at 700.0°C.

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

What is the value of Keq at this temperature for the following reaction?

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

A) 0.224

B) 0.335

C) 0.0125

D) 0.0560

E) 0.112

18) The Keq for the equilibrium below is 0.112 at 700.0°C.

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

What is the value of Keq at this temperature for the following reaction?

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

A) 0.224

B) 0.0125

C) 0.112

D) 8.93

E) -0.112

19) The Keq for the equilibrium below is 0.112 at 700.0°C.

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

What is the value of Keq at this temperature for the following reaction?

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

A) 79.7

B) 2.99

C) 17.86

D) 4.46

E) 8.93

20) Given the following reaction at equilibrium, if Kc = 1.90 × 1019 at 25.0°C, Kp = __________.

H2 (g) + Br2 (g) 2 HBr (g)

A) 5.26 × 10-20

B) 1.56 × 104

C) 6.44 × 105

D) 1.90 × 1019

E) none of the above

21) Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

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

A) [SO3] / [SO2][O2]

B) [SO2] / [SO3]

C) [SO3]2 / [SO2]2[O2]

D) [SO3]2 / [SO2]2[O2]2

E) [SO3] / [SO2][O2]2

22) Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

(NH4)2Se (s) 2NH3 (g) + H2Se (g)

A) [NH3][H2Se] / [(NH4)2Se]

B) [(NH4)2Se] / [NH3]2[H2Se]

C) 1 / [(NH4)2Se]

D) [NH3]2[H2Se]

E) [NH3]2[H2Se] / [(NH4)2Se]

23) Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

CO2 (s) + H2O (l) H+ (aq) + HCO3- (aq)

A) [H+][HCO3-] / [CO2]

B) [CO2] / [H+][HCO3-]

C) [H+][HCO3-] / [CO2][H2O]

D) [CO2][H2O] / [H+][HCO3-]

E) [H+][HCO3-]

24) Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

HF (aq) + H2O (l) H3O+ (aq) + F- (aq)

A) [HF][H2O] / [H3O+][F-]

B) 1 / [HF]

C) [H3O+][F-] / [HF][H2O]

D) [H3O+][F-] / [HF]

E) [F-] / [HF]

25) The expression for Kp for the reaction below is __________.

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

A)

B)

C)

D)

E)

26) The equilibrium-constant expression for the reaction

Ti (s) + 2Cl2 (g) TiCl4 (l)

is given by

A)

B)

C)

D) [Cl2 (g)]-2

E)

27) 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, __________.

A) products predominate

B) reactants predominate

C) roughly equal amounts of products and reactants are present

D) only products are present

E) only reactants are present

28) The equilibrium constant for the gas phase reaction

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

is Keq = 2.80 × 102 at 999 K. At equilibrium, __________.

A) products predominate

B) reactants predominate

C) roughly equal amounts of products and reactants are present

D) only products are present

E) only reactants are present

29) The equilibrium constant for the gas phase reaction

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

is Keq = 230 at 300°C. At equilibrium, __________.

A) products predominate

B) reactants predominate

C) roughly equal amounts of products and reactants are present

D) only products are present

E) only reactants are present

30) The equilibrium constant for the gas phase reaction

N2 (g) + O2 (g) 2NO (g)

is Keq = 4.20 × 10-31 at 30°C. At equilibrium, __________.

A) products predominate

B) reactants predominate

C) roughly equal amounts of products and reactants are present

D) only products are present

E) only reactants are present

31) Consider the following equilibrium.

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

The equilibrium cannot be established when __________ is/are placed in a 1.0-L container.

A) 0.25 mol SO2 (g) and 0.25 mol O2 (g)

B) 0.75 mol SO2 (g)

C) 0.25 mol of SO2 (g) and 0.25 mol of SO3 (g)

D) 0.50 mol O2 (g) and 0.50 mol SO3 (g)

E) 1.0 mol SO3 (g)

32) 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.

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

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

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

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

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

33) Which of the following statements is true?

A) Q does not change with temperature.

B) Keq does not change with temperature, whereas Q is temperature dependent.

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

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

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

34) How is the reaction quotient used to determine whether a system is at equilibrium?

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

B) At equilibrium, the reaction quotient is undefined.

C) The reaction is at equilibrium when Q < Keq.

D) The reaction is at equilibrium when Q > Keq.

E) The reaction is at equilibrium when Q = Keq.

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

A) H2 (g) + Cl2 (g) 2 HCl (g)

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

C) N2 (g) + 3 H2 (g) 2 NH3 (g)

D) 4 Fe (s) + 3 O2 (g) 2 Fe2O3 (s)

E) 2HI (g) H2 (g) + I2 (g)

36) Of the following equilibria, only __________ will shift to the right in response to a decrease in volume.

A) H2 (g) + Cl2 (g) 2 HCl (g)

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

C) N2 (g) + 3 H2 (g) 2 NH3 (g)

D) 2 Fe2O3 (s) 4 Fe (s) + 3 O2 (g)

E) 2HI (g) H2 (g) + I2 (g)

37) The reaction below is exothermic:

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

Le Châtelier’s Principle predicts that __________ will result in an increase in the number of moles of SO3 (g) in the reaction container.

A) increasing the pressure

B) decreasing the pressure

C) increasing the temperature

D) removing some oxygen

E) increasing the volume of the container

38) For the endothermic reaction

CaCO3 (s) CaO (s) + CO2 (g)

Le Châtelier’s principle predicts that __________ will result in an increase in the number of moles of CO2.

A) increasing the temperature

B) decreasing the temperature

C) increasing the pressure

D) removing some of the CaCO3 (s)

E) none of the above

39) In which of the following reactions would increasing pressure at constant temperature not change the concentrations of reactants and products, based on Le Châtelier’s principle?

A) N2 (g) + 3H2 (g) 2NH3 (g)

B) N2O4 (g) 2NO2 (g)

C) N2 (g) + 2O2 (g) 2NO2 (g)

D) 2N2 (g) + O2 (g) 2N2O (g)

E) N2 (g) + O2 (g) 2NO (g)

40) In which of the following reactions would increasing pressure at constant temperature change the concentrations of reactants and products, based on Le Châteliers principle?

A) N2 (g) + 3H2 (g) 2NH3 (g)

B) N2O4 (g) 2NO2 (g)

C) N2 (g) + 2O2 (g) 2NO2 (g)

D) 2N2 (g) + O2 (g) 2N2O (g)

E) all of the above

41) Consider the following reaction at equilibrium:

2NH3 (g) N2 (g) + 3H2 (g) ΔH° = +92.4 kJ

Le Châtelier’s principle predicts that adding N2 (g) to the system at equilibrium will result in __________.

A) a decrease in the concentration of NH3 (g)

B) a decrease in the concentration of H2 (g)

C) an increase in the value of the equilibrium constant

D) a lower partial pressure of N2

E) removal of all of the H2 (g)

42) Consider the following reaction at equilibrium:

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

Le Châtelier’s principle predicts that the moles of H2 in the reaction container will increase with __________.

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

B) a decrease in the total pressure (T constant)

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

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

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

43) Consider the following reaction at equilibrium:

2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier’s principle predicts that adding O2 (g) to the reaction container will __________.

A) increase the partial pressure of CO (g) at equilibrium

B) decrease the partial pressure of CO2 (g) at equilibrium

C) increase the value of the equilibrium constant

D) increase the partial pressure of CO2 (g) at equilibrium

E) decrease the value of the equilibrium constant

44) Consider the following reaction at equilibrium:

2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier’s principle predicts that an increase in temperature will __________.

A) increase the partial pressure of O2 (g)

B) decrease the partial pressure of CO2 (g)

C) decrease the value of the equilibrium constant

D) increase the value of the equilibrium constant

E) increase the partial pressure of CO

45) 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?

A) decreasing the partial pressure of H2O (g)

B) removing H2O (g) from the system

C) decreasing the volume of the reaction vessel

D) decreasing the pressure in the reaction vessel

E) increasing the amount of carbon in the system

46) Consider the following reaction at equilibrium.

2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier’s principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction __________.

A) at high temperature and high pressure

B) at high temperature and low pressure

C) at low temperature and low pressure

D) at low temperature and high pressure

E) in the presence of solid carbon

47) Consider the following reaction at equilibrium:

2SO2 (g) + O2 (g) 2SO3 (g) ΔH° = -99 kJ

Le Châtelier’s principle predicts that an increase in temperature will result in __________.

A) a decrease in the partial pressure of SO3

B) a decrease in the partial pressure of SO2

C) an increase in Keq

D) no changes in equilibrium partial pressures

E) the partial pressure of O2 will decrease

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

A) increase the rate of the forward reaction only

B) increase the equilibrium constant so that products are favored

C) slow the reverse reaction only

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

E) shift the equilibrium to the right

15.2 Bimodal Questions

1) The value of Keq for the equilibrium

H2 (g) + I2 (g) 2 HI (g)

is 794 at 25 °C. What is the value of Keq for the equilibrium below?

1/2 H2 (g) + 1/2 I2 (g) HI (g)

A) 397

B) 0.035

C) 28

D) 1588

E) 0.0013

2) The value of Keq for the equilibrium

H2 (g) + I2 (g) 2 HI (g)

is 794 at 25°C. At this temperature, what is the value of Keq for the equilibrium below?

HI (g) 1/2 H2 (g) + 1/2 I2 (g)

A) 1588

B) 28

C) 397

D) 0.035

E) 0.0013

3) The value of Keq for the equilibrium

H2 (g) + I2 (g) 2 HI (g)

is 54.0 at 427°C. What is the value of Keq for the equilibrium below?

HI (g) 1/2 H2 (g) + 1/2 I2 (g)

A) 27

B) 7.35

C) 0.136

D) 2.92 × 103

E) 3.43 × 10-4

4) The value of Keq for the equilibrium

CO2 (g) + 2H2 (g) CH3OH (g)

is 14.5 at 483 °C. What is the value of Keq for the equilibrium below?

1/2 CO2 + H2 (g) 1/2 CH3OH (g)

A) 7.30

B) 7.35

C) 0.136

D) 3.81

E) 6.90 × 10-2

5) The value of Keq for the equilibrium

N2 (g) + O2 (g) 2 NO (g)

is 4.2 × 10-31 at 27 °C. What is the value of Keq for the equilibrium below?

4 NO (g) 2 N2 (g) + 2 O2 (g)

A) 5.7 × 1060

B) 8.4 × 10-31

C) 4.2 × 1031

D) 8.4 × 1031

E) none of the above

6) Consider the following chemical reaction:

CO (g) + 2H2 (g) CH3OH(g)

At equilibrium in a particular experiment, the concentrations of CO and H2 were 0.15 M and0.36 M,respectively. What is the equilibrium concentration of CH3OH? The value of Keq for this reaction is 14.5 at the temperature of the experiment.

A) 14.5

B) 7.61 × 10-3

C) 2.82 × 10-1

D) 3.72 × 10-3

E) 1.34 × 10-3

7) A reaction vessel is charged with hydrogen iodide, which partially decomposes to molecular hydrogen and iodine:

2HI (g) H2(g) + I2(g)

When the system comes to equilibrium at 425 °C, PHI = 0.708 atm, and PH2 = PI2 = 0.0960 atm. The value of Kp at this temperature is __________.

A) 6.80 × 10-2

B) 1.30 × 10-2

C) 54.3

D) 1.84 × 10-2

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

8) 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] = 0.0990 M, [C2H3O2-] = 1.33 × 10-3 M, and [H+] = 1.33 × 10-3 M. The equilibrium constant, Keq, for the ionization of acetic acid at 25°C is __________.

A) 5.71 × 104

B) 0.100

C) 1.75 × 10-7

D) 1.79 × 10-5

E) 5.71 × 106

9) Dinitrogentetraoxide 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 __________.

A) 2.2 × 10-4

B) 13

C) 0.22

D) 0.022

E) 0.87

10) Given the following reaction:

CO (g) + 2H2(g) CH3OH (g)

In an experiment, 0.42 mol of CO and 0.42 mol of H2 were placed in a 1.00-L reaction vessel. At equilibrium, there were 0.29 mol of CO remaining. Keq at the temperature of the experiment is __________.

A) 2.80

B) 0.357

C) 14.5

D) 17.5

E) none of the above

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 __________.

A) 11

B) 4.0

C) 110

D) 6.1

E) 2.8

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.

A) 0.0782

B) 0.0455

C) 0.0908

D) 0.0330

E) 0.123

13) At 200°C, the equilibrium constant (Kp) for the reaction below is 2.40 × 103.

2NO (g) N2 (g) + O2 (g)

A closed vessel is charged with 36.1 atm of NO. At equilibrium, the partial pressure of O2 is __________ atm.

A) 294

B) 35.7

C) 17.9

D) 6.00

E) 1.50 × 10-2

15.3 Algorithmic Questions

1) Given the following reaction at equilibrium, if Kc = 6.34 x 105 at 230.0°C, Kp = __________.

2NO (g) + O2 (g) 2NO2 (g)

A) 3.67 × 10-2

B) 1.53 × 104

C) 6.44 × 105

D) 2.61 × 106

E) 2.62 × 107

2) Given the following reaction at equilibrium at 450.0°C:

CaCO3 (s) CaO (s) + CO2 (g)

If pCO2 = 0.0135 atm, Kc = __________.

A) 135

B) 0.0821

C) 0.801

D) 2.27 × 10-4

E) 8.01

3) Given the following reaction at equilibrium, if Kp = 0.990 at 250.0°C, Kc = __________.

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

A) 3.90 × 10-6

B) 2.31 × 10-2

C) 0.990

D) 42.9

E) 42.5

4) Given the following reaction at equilibrium at 300.0 K:

NH4HS (s) NH3 (g) + H2S (g)

If pNH3 = pH2S = 0.109 atm, Kp = __________.

A) .0119

B) 4.99 × 10-4

C) .109

D) .0821

E) 5.66 × 10-3

5) The Keq for the equilibrium below is 7.73 × 10-2 at 500.0°C.

2Cl2 (g) + 2H2O (g) 4HCl (g) + O2 (g)

What is the value of Keq at this temperature for the following reaction?

Cl2 (g) + H2O (g) 2HCl (g) + O2 (g)

A) 0.0773

B) 5.98 × 10-3

C) 0.278

D) 0.0376

E) 0.150

6) At 1000.0 K, the equilibrium constant for the reaction

2NO (g) + Br2 (g) 2NOBr (g)

is Kp = 0.017. Calculate Kp for the reverse reaction,

2NOBr (g) 2NO (g) + Br2 (g).

A) 0.017

B) 1.6 × 10-4

C) 59

D) 0.99

E) 1.1

7) 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

PPCl3 = 0.124 atm,

PCl2 = 0.157 atm, and

PPCl5 = 1.30 atm. What is the value of Kp at this temperature?

A) 66.7

B) 1.50 × 10-2

C) 2.53 × 10-2

D) 1.02

E) 4.63

8) Consider the following chemical reaction:

H2 (g) + I2 (g) 2HI (g)

At equilibrium in a particular experiment, the concentrations of H2, I2, and HI were 0.25 M, 0.035 M, and 0.55 M, respectively. The value of Keq for this reaction is __________.

A) 23

B) 63

C) 0.0090

D) 5.1

E) 34

9) 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 __________.

A) 0.723

B) 0.391

C) 0.212

D) 6.94 × 10-3

E) 1.92 × 10-4

10) The Kp for the reaction below is 1.49 × 108 at 100.0°C:

CO (g) + Cl2 (g) COCl2 (g)

In an equilibrium mixture of the three gases, PCO = PCl2 = 2.22 × 10-4 atm. The partial pressure of the product, phosgene (COCl2), is __________ atm.

A) 7.34

B) 3.02 × 1015

C) 3.31 × 10-16

D) 3.31 × 104

E) 6.67 × 1011

11) At 900.0 K, the equilibrium constant (Kp) for the following reaction is 0.345.

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

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.

A) 82.0

B) 4.21 × 10-3

C) 192

D) 6.20 × 10-4

E) 40.2

12) 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 0.556 mol of H2 present. At equilibrium, there are __________ mol of Br2 present in the reaction vessel.

A) 0.000

B) 0.440

C) 0.556

D) 0.126

E) 0.314

13) At 27°C, Kp = 0.095 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.

A) 0.31

B) 0.095

C) 0.052

D) 0.0049

E) 3.8

14) 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 0.16 mol of CO remaining. Keq at the temperature of the experiment is __________.

A) 5.5

B) 0.75

C) 0.93

D) 1.1

E) 1.0

15) 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 0.836 and 0.701 atm, respectively. The partial pressure of HI is __________ atm.

A) 7.87

B) 29.6

C) 5.44

D) 0.108

E) 0.0116

16) 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 0.36 mol of NOBr. How many moles of NO and Br2, respectively, are in the flask at equilibrium?

A) .28,.28

B) .36,.18

C) .28,.14

D) .14,.23

E) .36,.36

15.4 Short Answer Questions

1) The equilibrium-constant expression for a reaction written in one direction is the __________ of the one for the reaction written for the reverse direction.

2) If Reaction A + Reaction B = Reaction C, then Kc Reaction C = __________.

3) If the value for the equilibrium constant is much greater than 1, then the equilibrium mixture contains mostly __________.

4) Pure __________ and pure __________ are excluded from equilibrium-constant expressions.

5) Exactly 3.5 moles if N2O4 is placed in an empty 2.0-L container and allowed to reach equilibrium described by the equation

N2O4 (g) ⇌ 2NO2 (g)

If at equilibrium the N2O4 is 25% dissociated, what is the value of the equilibrium constant for the reaction?

6) The number obtained by substituting starting reactant and product concentrations into an equilibrium-constant expression is known as the __________.

7) If the reaction quotient Q for a reaction is less than the value of the equilibrium constant K for that reaction at a given temperature, __________ must be converted to __________ for the system to reach equilibrium.

8) If the reaction quotient Q for a reaction is greater than the value of the equilibrium constant K for that reaction at a given temperature, __________ must be converted to __________ for the system to reach equilibrium.

9) For an exothermic reaction, increasing the reaction temperature results in a(an) __________ in K.

10) If a reaction is endothermic, __________ the reaction temperature results in an increase in K.

15.5 True/False Questions

1) The relationship between the concentrations of reactants and products of a system at equilibrium is given by the law of mass action.

2) The effect of a catalyst on a chemical reaction is to react with product, effectively removing it and shifting the equilibrium to the right.

3) At constant temperature, reducing the volume of a gaseous equilibrium mixture causes the reaction to shift in the direction that increases the number of moles of gas in the system.

4) In an exothermic equilibrium reaction, increasing the reaction temperature favors the formation of reactants.

5) Le Châtelier’s principle states that if a system at equilibrium is disturbed, the equilibrium will shift to minimize the disturbance.

Answer:

 

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