Test Bank Chapter 14 Principles Of Chemical Equilibrium 676

CHAPTER 14

PRINCIPLES OF CHEMICAL EQUILIBRIUM

CHAPTER STUDY OBJECTIVES

1. Explain the dynamic nature of equilibrium in terms of reversibility.

SKILLS TO MASTER: Formulating the equilibrium expression for a given reaction

KEY CONCEPTS: At equilibrium, the rates of the forward and reverse reactions are equal. An equilibrium expression relates the concentrations of reactants and products at equilibrium. Every elementary reaction that goes in the forward direction can also go in the reverse direction.

2. Understand some of the properties of equilibrium constants.

SKILLS TO MASTER: Relating concentrations to activities; understanding the magnitudes of equilibrium constants

KEY CONCEPTS: Concentrations or partial pressures can usually be used in place of activities in equilibrium constant expressions. The activity of a pure solid or liquid is equal to 1.

3. Relate the equilibrium position to thermodynamic quantities.

SKILLS TO MASTER: Predicting the direction of change by comparing Q with K_eq; calculating the equilibrium constant from the reaction free energy change; calculating the equilibrium constant at non-standard temperatures

KEY CONCEPTS: Reactions always move in the direction that minimizes the total free energy.

4. Predict the effects on the equilibrium position of changing concentrations or temperature.

SKILLS TO MASTER: Determining the effects of increasing or decreasing the concentration of a reactant or product; determining the effects of changing the temperature

KEY CONCEPTS: When a change is imposed on a system at equilibrium, the system will react in the direction that reduces the amount of change (Le Chatelier’s principle).

5. Solve quantitative equilibrium problems.

SKILLS TO MASTER: Constructing concentration tables; using concentration tables to calculate equilibrium concentrations; doing equilibrium calculations with very small equilibrium constants; doing equilibrium calculations with very large equilibrium constants

KEY CONCEPTS: If initial concentrations and the equilibrium constant are known, equilibrium

concentrations can be calculated.

6. Perform equilibrium calculations on reactions in aqueous solution.

SKILLS TO MASTER: Identifying the major and minor species in solution; writing equilibrium expressions for acid and base hydrolysis reactions; writing solubility product and formation constant expressions

KEY CONCEPTS: In most aqueous solutions, there is one dominant equilibrium reaction. Spectator ions in solution undergo no significant reactions.

Multiple Choice QUESTIONS

1. A system in chemical equilibrium is characterized by one of the following:

a) molecules no longer undergo reactions of any kinds.

b) macroscopic changes are observed.

c) unaffected by changes in temperature.

d) unaffected by addition of catalyst.

e) concentrations are changing at a fixed constant rate.

Difficulty: Easy

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

2. A flask is filled with hydrogen, oxygen and several mL of water. This flask is then connected to a flask containing oxygen gas consisting of only the ¹⁷O isotope at the same pressure as the first flask. Which of the following will not occur?

a) Some water will evaporate.

b) The ¹⁷O₂ will diffuse into the other flask.

c) Hydrogen and water vapour will diffuse into the second flask.

d) ¹⁷O will be incorporated into the water.

e) ¹⁶O₂ will diffuse into the second flask.

Difficulty: Easy

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

3. The equilibrium constant

a) for an aqueous phase reaction is based on concentration of reactants and products.

b) for a gas phase reaction is based on pressures of the reactants and products.

c) is based on activities of all species.

d) is dependent on the initial concentrations of all species.

e) is dependent on the initial concentration of reactants only.

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

Feedback: Although equilibrium is often expressed in terms of pressure or concentration, this is an approximation; equilibria are based on activities.

4. When is a reaction at equilibrium?

a) when K = 1

b) when all concentrations are equal

c) when Q = 1

d) when all concentrations are equal to 1 M or 1 atm

e) when Q = K

Difficulty: Easy

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

5. The copper (I) ion is a curious species. In aqueous solutions, there are a number of reactions that it can undergo; one is the reaction with other copper(I) ions:

2 Cu⁺ (aq) Cu²⁺(aq) + Cu(s)

Using the tabulated data, calculate the equilibrium constant for this reaction of Cu⁺ (aq) at 298 and predict whether it will increase or decrease with increasing temperature. Choose from the following.

a) 3.5 x 10⁴; increase

b) 1.2 x 10^6; decrease

c) 2.2 x 10⁷ increase

d) 2.2 x 10⁷ decrease

e) 3.5 x 10⁴ decrease

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

6. Adding water to the reaction vessel in which the following reaction is occurring will result in

Ba(OH)₂•8H₂O_(s) + NH₄NO­_3(s) 🡪 Ba(NO₃)_2(s) + H­₂O_(l) + NH_3(aq)

a) no change.

b) reaction will shift right as the concentration of NH₃ is decreased.

c) reaction will shift to the left as more product is added.

d) reaction will shift to the right as more product is added.

e) reaction will shift left as the concentration of NH₃ is increased.

Difficulty: Medium

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

Feedback: Must recognize that while water does not enter the equilibrium expression; it will have an effect on concentration of dissolved species.

7. If the dissolution of CaCl₂ is endothermic, will any of the following increase the amount of CaCl₂ that will dissolve in water?

a) addition of NaCl

b) addition of Ca(NO₃)₂

c) addition of HCl

d) increase in temperature

e) decrease in temperature

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

8. Which of the following will decrease the amount of [NH₄][NO₃] that will dissolve in water?

a) addition of NaCl

b) addition of Ca(NO₃)₂

c) addition of HCl

d) addition of NaOH

e) increase the pressure

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

9. A system containing nitrogen, ammonia, and hydrogen is at equilibrium. The exothermic reaction will shift to greater production of ammonia if

a) H₂ is added.

b) NH₃ is added.

c) Ar is added.

d) a catalyst is added.

e) the temperature is increased.

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

10. Which way will the Haber process shift if a container at equilibrium has its volume decreased?

N₂ + 3 H₂ 2 NH₃

a) Shift to the reactants.

b) Shift to the products.

c) There will be no change.

d) The temperature will increase.

e) Initially will shift to the products, then readjust to original pressures.

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

11. Which way will the Haber process (a spontaneous reaction) shift if the temperature of a container at equilibrium is raised?

N₂ + 3 H₂ 2 NH₃

a) Shift to the reactants.

b) Shift to the products.

c) There will be no change.

d) The rate of the reaction will increase.

e) Initially will shift to the products, then readjust to original pressures.

Difficulty: Medium

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

Feedback: Students must recognize that since the Haber process is spontaneous, it must also be exothermic; increasing temperature of an exothermic reaction shifts equilibrium toward reactants.

12. When solving equilibrium problems the best way to simplify the problem is to

a) apply approximations.

b) use the quadratic equation.

c) approach equilibrium from the side from which the change is smallest.

d) divide by zero.

e) find the rate-determining step.

Difficulty: Easy

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

13. When 0.1 mole of methylamine is dissolved in 500 mL of water, the following hydrolysis reaction occurs:

H₂O_(l) + CH₃NH_2(aq) CH₃NH₃⁺_(aq) + OH^-_(aq)

The hydroxide concentration is found to be 8.6 x10^-3 M when equilibrium is reached. What is the value of the equilibrium constant for this reaction?

a) 4.3 x 10^-2

b) 7.4 x10^-4

c) 7.4 x 10^-5

d) 3.9 x 10^-4

e) 7.4 x 10^-3

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

14. When ammonia dissolves in water the new major species present are

a) H₂O; NH₂^-; H⁺

b) H₂O; NH₃

c) H₂O; NH₄⁺; OH^-

d) H₂O; NH^2-; H⁺

e) H₂O; N^3-; H⁺

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

15. Addition of sodium mono-hydrogencarbonate to water gives what minor species?

a) H₂O; Na⁺; H⁺; CO₃^2-

b) H₂O; Na⁺; OH^-; H₂CO₃

c) H₂O; NaHCO₃

d) H₂O; Na⁺; H₃CO₃^+; OH^-

e) H₂O; Na⁺; HCO₃^-

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

16. Addition of sodium mono-hydrogencarbonate to water gives what major species?

a) H₂O; H⁺; CO₃^2-

b) H⁺, CO₃^2-, OH^-; H₂CO₃

c) NaHCO₃

d) H₂O; Na⁺; H₂CO₃, OH^-

e) H₂O; Na⁺; HCO₃^-

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

17. What are the minor species present upon adding the slightly soluble PbCl_2(s) to water?

a) H₂O; Pb⁺², Cl^-, Cl₂^2-

b) Pb⁺², Cl^-, Cl₂^2-

c) Pb⁺², Cl^-

d) H₂O; Pb⁺², Cl^-

e) PbCl₂(s)

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

18. Ammonia and aqueous HCl are combined in an Erlenmeyer flask. Which of the following reactions occurs?

a) precipitation reaction

b) donation of a proton to water

c) dissociation of a complex

d) donation of a proton to a base

e) dissolution of a salt in water

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

19. Classify the equilibrium constant for the following reaction as:

Ag⁺_(aq) + 2 NH­­_3(aq) Ag(NH₃)₂⁺_(aq)

a) K_sp

b) K_ion­

c) K_f

d) K_a

e) K_b

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

20. Classify the equilibrium constant for the following reaction as:

CH₃NH_2(aq) + H₂O_(l) CH₃NH­₃⁺_(aq) + OH^-_(aq)

a) K_sp

b) K_ion­

c) K_f

d) K_a

e) K_b

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

21. Classify the equilibrium constant for the following reaction as:

Fe(OH)_­3(s) Fe⁺³_(aq) + 3 OH^-_(aq)

a) K_sp

b) K_ion­

c) K_f

d) K_a

e) Kb

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

ESSAY QUESTIONS

22. In the manufacture of ammonia, nitrogen molecules dissociate to give nitrogen atoms on the surface of the catalyst. Draw a molecular picture showing the reverse of this process.

Difficulty: Easy

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

23. Draw a graph of concentration vs. time for a system containing cis- and trans-butene in equilibrium (assume the equilibrium constant is 3.0) to which is added an amount of trans-butene equal to that present in the original mixture and monitored until equilibrium is reached again.

Difficulty: Medium

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

24. Acetic acid dissolves in water and undergoes the following reaction to increase the concentration of hydronium ions:

CH₃COOH (aq) 🡪 H₃O⁺ (aq) + CH₃COO- (aq) k₁

Express the equilibrium constant in terms of the rate constants of this elementary process and its reverse.

H₃O⁺ (aq) + CH₃COO- (aq) 🡪 CH₃COOH (aq) k_-1

Difficulty: Hard

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

25. What is the concentration based equilibrium constant for

4NO₂(g) + O₂(g) 🡪 2N₂O₅(g)?

Difficulty: Easy

Learning Objective: Explain the dynamic nature of equilibrium in terms of reversibility.

Section Reference: 14.1 Describing Chemical Equilibria

26. Write the equilibrium constant expression for the following reaction:

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

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

Feedback: based on pressure not concentration

27. Write the equilibrium constant expression for the following reaction:

C₂H₄ (g) + 2HCl (g) + O₂ (g) CH₂ClCH₂Cl (g) + H₂O (g)

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

Feedback: based on pressure not concentration

28. Write the equilibrium constant expressions for the following reaction:

N₂(g) + 3 H₂(g) 2 NH₃(g)

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

Feedback: based on pressure not concentration

29. Write the equilibrium constant expression and state the reference concentrations for the reaction: CaCO₃(s) CaO(s) + CO₂(g)

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

30. Write the equilibrium constant expressions and state the reference concentrations for the reactants and products:

Cl₂ (g) + 2 H₂O (l ) HOCl (aq) + Cl- (aq) + H₃O⁺ (aq)

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

31. Write the equilibrium constant expression for the following reaction:

HCOOH_(aq) + H₂O_(l) H₃O⁺_(aq) + HCOO^-1_(aq)

Difficulty: Easy

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

32. Write the equilibrium constant expression for the following reaction in terms of concentrations:

2 PbS_(s) + 3 O₂(g) 2 PbO_(s) + 2 SO_2(g)

Difficulty: Easy

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

33. Write the combined equilibrium constant expression for the following proposed reaction mechanism of the reaction between NO₂ and CO:

NO_2(g) + NO_2(g) NO_3(g) + NO_(g)

NO_3(g) + CO_(g) CO_2(g) + NO_2(g)

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

34. The equilibrium constant for the following reaction is given:

4 NO_2(g) 2 N₂O_(g) + 3 O_2(g) K₁ = 690

What is the value for the equilibrium constant of the reverse reaction?

2 N₂O_(g) + 3 O_2(g) 4 NO_2(g) K₂ =?

Difficulty: Easy

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

35. Based on the following two reactions and equilibrium constants, determine the value of K­_3­­.

I. NO_(g) + ½ O_2(g) NO_2(g) K₁ = 1.3 x 10⁶

II. ½ N_2(g) + ½ O_2(g) NO_(g) K₂ = 6.5 x 10^-16

N_2(g) + 2 O_2(g) 2 NO_­2(g) K₃ =?

Difficulty: Medium

Learning Objective: Understand some of the properties of equilibrium constants.

Section Reference: 14.2 Properties of Equilibrium Constants

36. Calculate the equilibrium constant for the oxychlorination of ethylene to vinyl chloride, CH₂CHCl, under standard conditions at 100^oC given the thermodynamic data below collected at 25^oC:

ΔG˚ = 53.6(CH₂CHCl), –95.3(HCl), 68.49(CH₂CH₂), –228.7(H₂O) kJ/mol

ΔH˚ = 37.2(CH₂CHCl), –92.3(HCl), 52.4(CH₂CH₂), –241.8(H₂O) kJ/mol

The equation of reaction is:

CH₂CH_{2 (g)} + HCl _(g) + O_{2 (g)} 🡪 CH₂CHCl _(g) + H₂O _(g)

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

Feedback: This problem requires several steps. Must calculate ΔG^o and ΔH^o at 25ºC from data given and use this to determine ΔS^o. The values of ΔH^o and ΔS^o can then be used to find ΔG^o at 100^oC (373ºK) and subsequently K; alternatively one can calculate ΔG^o and ΔH^o and K at 298; and then calculate K at 373ºK.

37. The dehydration of benzyl alcohol to benzaldehyde is shown below:

C₆H₅CH₂OH_(g) C₆H₅CHO_(g) + H_2(g)

The equilibrium constant for this process is 0.558 at 525 K. 0.2 moles of benzyl alcohol is placed in a 2L flask with 0.15 moles benzaldehyde and 0.1 moles of H₂ gas. Determine Q for this mixture and which direction the reaction will shift to reach equilibrium.

Difficulty: Medium

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

Feedback: Equilibrium constant is based on pressures for gas phase reactions.

38. Calcite, CaCO_3(s), can be converted to CaO_(s) and CO_2(g). Determine the equilibrium constant at 25^oC and predict whether equilibrium favours the products or the reactants.

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

Feedback: Challenging multistep problem requiring mastery of concepts from Chapter 11. Must first determine ΔG˚ using thermodynamic data, then calculate the equilibrium constant.

39. Calcite, CaCO_3(s), can be converted to CaO_(s) and CO_2(g). What is the equilibrium pressure of CO₂ at 1150ºK?

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

Feedback: Challenging multi-step problem requiring mastery of concepts from Chapter 11. Must first determine ΔG˚ using thermodynamic data at 1150ºK, then determine the equilibrium constant and recognize that solids do not enter the equilibrium expression.

40. Determine the equilibrium constant at 0^oC for the following unbalanced reaction:

Ba(OH)₂•8H₂O_(s) + NH₄NO­_3(s) 🡪 Ba(NO₃)_2(s) + H­₂O_(l) + NH_3(aq)

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

Feedback: Challenging multi-step problem requiring mastery of concepts from Chapter 11 and beginning with balancing of the chemical equation. Must first determine ΔG˚ using thermodynamic data at 0ºK, then determine the equilibrium constant and recognize that solids do not enter the equilibrium expression.

41. The “water gas shift reaction” is shown below. Calculate K at (a) 1000ºK and (b) find the temperature at which the equilibrium constant is 1.

CO (g) + H₂O (g) CO₂ (g) + H₂ (g)

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

42. Consider the dissociation of mono-hydrogen carbonate to carbonate and aqueous hydrogen ion:

H₂O_(l) + HCO₃^- (aq) H₃O⁺ (aq) + CO₃^2- (aq)

ΔG˚ = (–237.1) (–586.77) (–237.1) (–527.8) kJ/mol

a) Calculate ∆G° for this reaction.

b) Calculate ∆G for the same reaction, where [CO₃^2-]=[HCO₃^-] = 1 M and [H⁺] = 1 x 10^-11 M. Under which conditions will this reaction be spontaneous?

Difficulty: Medium

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

43. Water undergoes dissociation as shown below:

2 H₂O (aq) H₃O⁺ (aq) + OH^- (aq)

ΔG˚ = (–237.1) (–237.1) (–157.244) kJ/mole

Find K for this reaction at 25˚C and 99˚C.

Difficulty: Hard

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

44. Lead chloride is not very soluble in water:

PbCl₂ (s) Pb²⁺(aq) + 2 Cl^- (aq)

Using the tabulated data, find the equilibrium constants for dissolution of PbCl₂ at 298º and 372ºK, respectively.

Difficulty: Medium

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

45. H₂PO₄^-1 is commonly used in making buffer solutions with a pH near your body’s pH. Given that K_a = 6.2 x10^-8 at 25˚C for the following acid-base reaction, determine ΔG˚:

H₂PO₄^-1_(aq) + H₂O_(l) HPO₄^-2_(aq) + H₃O⁺_(aq)

Difficulty: Easy

Learning Objective: Relate the equilibrium position to thermodynamic quantities.

Section Reference: 14.3 Thermodynamics and Equilibrium

46. Predict whether each equilibrium reaction will shift toward products or reactants with a decrease in temperature.

(a) CH₄ + H₂O CO + 3 H₂ ∆H° = 206 kJ

(b) 2 SO₂ + O₂ 2 SO₃ ∆H° = – 198 kJ

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

47. What will be the shift in equilibrium for the following reaction upon increasing temperature?

N₂ (g) + O₂ (g) 2 NO (g) ∆H° = 90.3 kJ

Difficulty: Easy

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

48. A system containing nitrogen, ammonia and hydrogen is at equilibrium. If the partial pressures of the gases remain the same immediately upon addition of Ar, what will the equilibrium do to re-establish equilibrium?

N₂ + 3 H₂ 2 NH­­_3­

Difficulty: Medium

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

49. Water undergoes self dissociation as below:

2 H₂O (aq) H₃O⁺ (aq) + OH^- (aq)

If K increases as temperature increases, determine if this reaction is endothermic or exothermic and explain.

Difficulty: Medium

Learning Objective: Predict the effects on the equilibrium position of changing concentrations or temperature.

Section Reference: 14.4 Shifts in Equilibrium

50. A sample of 3.00 x 10^-1 mole of pure phosgene gas, COCl₂, was placed in a 15.0 L container and heated to 800ºK. At equilibrium, the partial pressure of CO was found to be 0.497 bar. Calculate the equilibrium constant for the following reaction:

COCl_{2 (g)} CO _(g) + Cl_{2 (g)}

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

51. A sample of pure phosgene, COCl₂, is placed in a 15.0 L container which is subsequently heated to 800ºK. The equilibrium constant for the decomposition of phosgene at 800ºK is 0.297, and the equilibrium mixture contains 1.1 x 10^-1 moles of Cl₂(g), what are the equilibrium partial pressures of phosgene and carbon monoxide and how many moles of phosgene were placed in the original sample?

COCl_{2 (g)} CO _(g) + Cl_{2 (g)}

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

Feedback: multi-step process requiring application of ideal gas law from Chapter 2

52. The conversion of nitrogen and hydrogen to ammonia is an important industrial reaction:

N_{2 (g)} + 3 H_{2 (g)} 2 NH_{3 (g)}

If a tank initially containing only nitrogen at 1.0 atm and hydrogen at 3.0 atm converts 13.0 % of the nitrogen to ammonia, what is the value of the equilibrium constant for the reaction at this temperature?

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

53. Heating isopropyl alcohol causes it to break down to acetone and hydrogen gas:

(CH₃)₂CHOH_(g) (CH₃)₂CO_(g) + H_2(g)

At 180˚C, the equilibrium constant is 0.444 for this dehydrogenation reaction. If 10.0 grams of isopropyl alcohol is placed in a 10.0-L vessel and heated, what will be the partial pressure of acetone when equilibrium is reached?

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

54. Heating isopropyl alcohol causes it to break down to acetone and hydrogen gas:

(CH₃)₂CHOH_(g) (CH₃)₂CO_(g) + H_2(g)

If 20.0 g of isopropyl alcohol is placed in a 20.0 L vessel and heated to 180^oC, the partial pressure of acetone stabilizes at 0.35 atm. What is the equilibrium constant?

Difficulty: Medium

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

55. Heating isopropyl alcohol causes it to break down to acetone and hydrogen gas:

(CH₃)₂CHOH_(g) (CH₃)₂CO_(g) + H_2(g)

If 20.0 g of isopropyl alcohol is placed in a 20.0 L vessel and heated to 180^oC. The final pressure in the vessel is 0.96 atm, what is the equilibrium constant?

Difficulty: Medium

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

56. The water gas shift reaction is used to remove CO from the mixture of gases in ammonia production:

CO _(g) + H₂O _(g) CO_{2 (g)} + H_{2 (g)}

At 300°C, the equilibrium constant for this reaction has K = 36. If a tank with a volume of 30.0 L is charged with 1.0 mole of CO and 2.2 mols of H₂O and the temperature brought to 300°C, what are the equilibrium pressures of CO, H₂, H₂O and CO₂ in the tank?

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

57. At 1033ºK, K = 33.3 M for the equilibrium reaction:

PCl_{5 (g)} PCl_{3 (g)} + Cl_{2 (g)}

If a mixture of 0.100 mole of PCl₅ and 0.300 mole of PCl₃ is placed in a 2.00 L reaction vessel and heated to 1033ºK, what are the numbers of mols of each component at equilibrium?

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

58. HCO₃^-1 is used by your body to maintain pH levels in the blood. If the original concentration of [HCO₃^-1] = 0.0020M, determine the concentration of H­­₃O⁺ given K_eq = 4.7 x10^-11.

HCO₃^-1_(aq) + H_­2O_(l) H₃O⁺_(aq) + CO₃^-2_(aq)

Difficulty: Hard

Learning Objective: Solve quantitative equilibrium problems.

Section Reference: 14.5 Working with Equilibria

59. A solution contains 0.01 M Ag and 0.1 M Pb²⁺. NaCl is gradually added to precipitate the Ag⁺ as AgCl, and the Pb²⁺ as PbCl₂. Given the following K_sp values: AgCl (K_sp = 1.6 x 10^-10) PbCl₂ (K_sp = 2.4 x 10^-4). What is the concentration of Ag⁺ when the Pb²⁺ begins to precipitate?

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

Feedback: Relatively straight forward multi-step problem including writing the balanced precipitation reactions, determining the chloride concentration required for precipitation of PbCl₂, and subsequently determining the concentration of Ag⁺ at this Cl^- concentration.

60. The K_sp of PbBr₂ is 8.9 x 10^-6. If enough PbBr₂ salt is added to saturate the following solutions, determine the equilibrium concentration of Pb²⁺ in pure water and in 0.20 M KBr.

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

61. Solid CaF₂ is added to a 0.10 M solution of CaCl₂ until no more will dissolve. If the K_sp of CaF₂ is 3.9 x 10^-11 M³, what are the concentrations of Ca²⁺ _(aq) and F-_(aq) at equilibrium?

Difficulty: Medium

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

62. A sample of 0.134 g of CuCl₂•2H₂O is added to 0.10 L of an 1.0 M ammonia solution. It completely dissolves to give aqueous Cu²+ ions which react with the ammonia to form the coppertetraammine complex ion:

Cu²⁺ _(aq) + 4 NH_{3 (aq)} Cu(NH₃)₄²⁺_(aq) Kf = 5.0 x 10¹³

What are the concentrations of copper (II), ammonia, and the complex ion, Cu(NH₃) ₄²⁺, at equilibrium?

Difficulty: Hard

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

63. What are the major species present upon dissolving glucose (C₆H₁₂O₆) in water?

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

64. Solid silver chloride is added to two beakers, one containing 0.5 M NaNO₃ and the other 0.5 M NaCl. In which will the silver ion concentration be higher?

Difficulty: Easy

Learning Objective: Perform equilibrium calculations on reactions in aqueous solution.

Section Reference: 14.6 Equilibria in Aqueous Solutions

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