Equilibrium Worksheets

for

Chemistry 12

Notes Worksheets Quiz

1. Approaching Equilibrium WS 1 Q1

2. LeChatelier's Principle-1 WS 2

3. LeChatelier's Principle-2 WS 3 & 4 Q2

4. LeChatelier's-3 & Start Lab WS 5

5. Lab Lechatelier's Questions 1-10 Conclusion

6. Haber/Graphing WS 6 & 7 Q3

7. Equilibrium Constants WS 8 Q4

8. Keq Calculations WS 9 & 10

9. K-trial & Size Keq WS 11 Q5

10. Entropy & Enthalpy WS 12 Q6

11. Review Web Review Practice Test 1

12. Review Practice Test 2 Quizmebc

The following workbook will ensure that you can demonstrate your understanding of all aspects of the kinetics unit. The minimum expectation is that you do all of these questions by the due dates given by your teacher. There are other things that you should do to prepare for the test at the end of the unit. Remember, what you put into this course is what you will get out. There is no substitute for consistent effort and hard work. If you cannot do a question, get some help before the end of the unit, you need to know, understand, and remember everything. Good luck! I know you can do well in this unit.

Worksheet #1 Approaching Equilibrium

1. What are the conditions necessary for equilibrium?

2. What is a forward reaction versus a reverse reaction?

3. Why does the forward reaction rate decrease as equilibrium is approached?

4. What are the characteristics of equilibrium?

5. Define equilibrium.

6. Define the word dynamic and explain its relevance to the concept of equilibrium.

7. Why does the reverse reaction rate increase as equilibrium is approached?

As a reaction is approaching equilibrium describe how the following change. Explain what causes each change.

8. Reactant concentration.

9. Products concentration.

10. Forward reaction rate.

11. Reverse reaction rate.

12. What is equal at equilibrium?

13. What is constant at equilibrium?

14. Sketch each graph to show how concentrations change as equilibrium is approached

15. Label each graph with the correct description.

· The forward and reverse rates as equilibrium is approached

· The overall rate as equilibrium is approached

· The reactant and product concentrations as equilibrium is approached (two graphs)

16. Draw a PE Diagram for the reaction if PE of the reactants is 100 KJ/mole N₂O₄ and

Ea = 110 KJ/mole N₂O_4.

N₂O_{4 (g)} ⇄ 2 N0_{2 (g)} DH= +58KJ

(colorless) (brown)

If a catalyst were added to the reaction, what would happen to the PE Diagram, the forward rate, and the reverse rate?

PE Diagram Forward rate Reverse rate

One mole of very cold, colorless N₂O_{4 (g)} is placed into a 1.0L glass container of room temperature. The reaction:

N₂O_{4 (g)} ⇄ 2 N0_{2 (g)} DH= +58 KJ

(colorless) (brown)

proceeds to equilibrium. The concentration of each gas is measured as a function of time.

Time (s) 0 5 10 15 20 25

[N₂O₄] (M) 1.0 0.83 0.81 0.80 0.80 0.80

[N0₂] (M) 0.0 0.34 0.38 0.40 0.40 0.40

17. Plot concentration of N₂O₄ and N0₂ against time on the same graph below.

1.0 -

0.9 -

0.8 -

0.7 -

0.6 -

0.5 -

0.4 -

0.3 -

0.2 -

0.1 -

0.0 -

0 5 10 15 20 25 30 35

TIME (s)

18. After what time interval has equilibrium been established? ___________

19. Describe the change in the appearance of the container over 25 seconds (describe the colour change and when it becomes constant).

20. Calculate the rate of N₂O₄ consumption in (M/s) over the first 5s period and then the second 5s period.

0-5 sec. rate = ________M/s

5-10 sec. rate = ________M/s

Why is the rate greater over the first five minutes compared to the second five minutes (think in terms of reactant and product concentrations?

21. Calculate the rate of N0₂ production in (M/s) over the first 5s period and then the second 5s period.

0-5 sec. rate = ________M/s

5-10 sec. rate = ________M/s

How does the rate of formation of N0₂ compare to the rate of consumption of N₂O₄? Remember, if you measure the reactants or products, it is still the overall rate.

22. What are the equilibrium concentrations of N₂O₄ and N0₂?

[N₂O₄]= ______M Are they equal? ______!

[N0₂] = ______M

23. Is the reaction over, when equilibrium has been achieved? If not, explain.

24. What are the necessary conditions to establish equilibrium?

25. What are the characteristics of an equilibrium?

Worksheet #2 LeChatelier’s Principle

Describe the changes that occur after each stress is applied to the equilibrium.

N_{2 (g)} + 3H_{2 (g)} ⇄ 2NH_3(g) + 92 KJ

Shifts Shifts to the

Stress [N₂] [H₂] [NH₃] Right or Left Reactants or Product

1. [N₂] is increased

2. [H₂] is increased

3. [NH₃] is increased

4. Temp is increased

5. [N₂] is decreased

6. [H₂] is decreased

7. [NH₃] is decreased

8. Temp is decreased

9. A catalyst is added

N₂O_{4 (g)} ⇄ 2NO_2(g) DH = + 92 KJ

Shifts Shifts to Favour the

Stress [N₂O₄] [NO₂] Right or Left Reactants or Products

1. [N₂O₄] is increased

2. [NO₂] is increased

3. Temp is increased

4. [N₂O₄] is decreased

5. [H₂] is decreased

6. [NO₂] is decreased

7. Temp is decreased

4HCl _(g) + O_{2 (g)} ⇄ 2H₂O_(g) + 2Cl_{2 (g)} + 98 KJ

Shifts Shifts to Favour the

Stress [O₂] [H₂O] [HCl] Right or Left Reactants or Products

1. [HCl] is increased

2. [H₂O] is increased

3. [O₂] is increased

4. Temp is increased

5. [H₂O] is decreased

6. [HCl ] is decreased

7. [O₂] is decreased

8. Temp is decreased

9. A catalyst is added

CaCO_{3 (s)} + 170 KJ ⇄ CaO _(s) + CO_{2 (g)}

Note : Adding solids or liquids and removing solids or liquids does not shift the equilibrium. This is because you cannot change the concentration of a pure liquid or solid as they are 100% pure. It is only a concentration change that will change the # of collisions and hence shift the equilibrium.

Shifts Shifts to Favor the

Stress [CO₂] Right or Left Reactants or Products

1. CaCO₃ is added

2. CaO is added

3. CO₂ is added

4. Temp is decreased

5. A catalyst is added

6. [CO₂] is decreased

7. Temp is increased

8. CaO is removed

Worksheet #3 Applying Le Châtelier's Principle

The oxidation of ammonia is a reversible exothermic reaction that proceeds as follows:

4 NH_{3 (g)} + 5 O_{2 (g)} ⇄ 4 NO _(g) + 6 H₂O _(g)

For each situation described in the table, indicate an increase or decrease in overall concentration from before to after a new equilibrium has been established.

Component Stress Equilibrium Concentrations

NH₃] [O₂] [NO] [H₂O]

NH₃ addition

removal

O₂ addition

removal

NO addition

removal

H₂O addition

removal

[NH₃] [O₂] [NO] [H₂O]

Increase in temperature

Decrease in temperature Increase in pressure

Decrease in pressure

Addition of a catalyst

An Inert gas is added

Worksheet #4 Le Chatelier’s Principle

State the direction in which each of the following equilibrium systems would be shifted upon the application of the following stress listed beside the equation.

1. 2 SO_{2 (g)} + O_{2 (g)} ⇄ 2 SO_{3 (g)} + energy decrease temperature

2. C _(s) + CO_{2 (g)} + energy ⇄ 2 CO _(g) increase temperature

3. N₂O_{4 (g)} ⇄ 2 NO_{2 (g)} increase total pressure

4. CO _(g) + H₂O _(g) ⇄ CO_{2 (g)} + H_{2 (g)} decrease total pressure

5. 2 NOBr _(g) ⇄ 2 NO _(g) + Br_{2 (g)} decrease total pressure

6. 3 Fe _(s) + 4 H₂O _(g) ⇄ Fe₃O_{4 (s)} + 4 H_{2 (g)} add Fe_(s)

7. 2 SO_{2 (g)} + O_{2 (g)} ⇄ 2 SO_{3 (g)} add catalyst

8. CaCO_{3 (s)} ⇄ CaO _(s) + CO_{2 (g)} remove CO_{2 (g)}

9. N_{2 (g)} + 3 H_{2 (g)} ⇄ 2 NH_{3 (g)} He is added

Consider the following equilibrium system:

3 H_{2 (g)} + N_{2 (g)} ⇄ 2 NH_{3 (g)} + Heat.

State what affect each of the following will have on this system:

10. More N₂ is added to the system

11. Some NH₃ is removed from the system

12. The temperature is increased

13. The volume of the vessel is increased

14. A catalyst was added

15. An inert gas was added at constant

If a catalyst was added to the above reaction and a new equilibrium was established. Compare to the original system, the rates of the forward and reverse reactions of the new equilibrium.

Forward Rate has Reverse Rate has

16. If the temperature was increased in the above reaction and a new equilibrium was established. Compare to the original system, the rates of the forward and reverse reactions of the new equilibrium.

Forward Rate has Reverse Rate has

17. If the volume of the container was increased in the above reaction and a new equilibrium

was established. Compare to the original system, the rates of the forward and reverse reactions of the new equilibrium.

Forward Rate has Reverse Rate has .

Consider the following equilibrium system

H_{2 (g)} + I_{2 (g)} ⇄ 2 HI _(g)

State what affect each of the following will have on this system in terms of shifting.

18. The volume of the vessel is increased

19. The pressure is increased

20. A catalyst is added

Consider the following equilibrium system:

3 Fe _(s) + 4 H₂O _(g) ⇄ Fe₃O_{4 (s)} + 4 H_{2 (g)}

State what affect each of the following will have on this system in terms of shifting.

21. The volume of the vessel is decreased

22. The pressure is decreased

23. More Fe is added to the system

24. Some Fe₃O₄ is removed from the system

25. A catalyst is added to the system

Consider the following equilibrium:

2NO _(g) + Br_{2 (g)} + energy ⇄ 2NOBr _(g)

State what affect each of the following will have on this system in terms of shifting.

26. The volume of the vessel is increased

27. The pressure is decreased

28. More Br₂ is added to the system

29. Some NO is removed from the system

30. A catalyst is added to the system

Some CO was added to the system and a new equilibrium was established.

2CO _(g) + O_{2 (g)} ⇄ 2CO_{2 (g)} + energy

31. Compared to the original system, the rates of the forward and reverse reactions of the new equilibrium. Forward Rate has Reverse Rate has

32. Compared to the original concentrations, after the shift, have the new concentrations increased or decreased?

[CO] [O₂] [CO₂]

33. Did the equilibrium shift favour the formation of reactants or products?

A catalyst was added to the system at constant volume and a new equilibrium was established. 2CO _(g) + O_{2 (g)} ⇄ 2CO_{2 (g)} + energy

34. Compared to the original system, the rates of the forward and reverse reactions of the new equilibrium. Forward Rate has Reverse Rate has

35. Compared to the original concentrations, after the shift, have the new concentrations increased or decreased?

[CO] [O₂] [CO₂]

36. Did the equilibrium shift favour the formation of reactants or products?

The volume of the container was decreased and a new equilibrium was established. 2CO _(g) + O_{2 (g)} ⇄ 2CO_{2 (g)} + energy

37. Compare to the original system, the rates of the forward and reverse reactions of the new equilibrium. Forward Rate has Reverse Rate has

38. Compared to the original concentrations, after the shift, have the new concentrations increased or decreased?

[CO] [O₂] [CO₂]

39. Did the equilibrium shift favor the formation of reactants or products?

Worksheet #5 Applying Le Châtelier's Principle

1. The chromate and dichromate ions set up an equilibrium system as follows:

energy + 2 CrO₄ ^2-_(aq) + 2 H⁺_(aq) ⇄ Cr₂O₇ ^2-_(aq) + H₂O _(l)

yellow orange

Describe how the above equilibrium will shift after each stress below:

shift color change

Increase in [H⁺]

Increase in [CrO₄ ^2-]

Increase in [Cr₂O₇ ^2-]

Decrease in [H⁺]

Decrease in [CrO₄ ^2-]

Increase in temperature

Decrease in temperature

Add HCl _(aq)

Add NaOH

2. The copper (II) ion and copper (II) hydroxide complex exist in equilibrium as follows:

Cu(OH)_{2 (aq)} + 4 H₂O _(l) ⇄ Cu(H₂O)₄ ²⁺_(aq) + 2 OH^-_(aq) + 215 kJ

violet light blue

Describe how the above equilibrium will shift after each stress below:

shift color change

Increase in [Cu(H₂O)₄ ²⁺]

Add NaOH

Increase in [Cu(OH)₂]

Decrease in [Cu(H₂O)₄ ²⁺]

Decrease in [Cu(OH)₂]

Increase temperature

Decrease temperature

Add KCl _(aq)

Add HCl _(aq)

3. Consider the equilibrium that follows:

4 HCl _(g) + 2 O_{2 (g)} ⇄ 2 H₂O _(l) + 2 Cl_{2 (g)} + 98 kJ

(clear) (yellow)

Describe how the above equilibrium will shift after each stress below:

shift color change

Increase in temperature

Increase [HCl]

Decrease in [Cl₂]

Decrease temperature

Add Ne at constant volume

4. Consider the equilibrium that follows:

Cu⁺ _(aq) + Cl^-_(aq) ⇄ CuCl _(s) ΔH = + 98 kJ

(green)

Describe how the above equilibrium will shift after each stress below:

Cu⁺ is green

shift color change

Increase in temperature

Increase [HCl]

Add NaCl

Decrease temperature

Add NaOH _(aq)

(check your solubility table for a possible reaction)

Add CuCl_(s)

Add AgNO_{3 (aq)}

(check your solubility table for a possible reaction)

Add CuNO_{3 (aq)}

Add Cu(NO₃)_{2 (aq)}

Worksheet #6 Graphing and LeChatelier’s Principle

Consider the following equilibrium system.

I_2(g) + Cl_2(g) ⇄ 2 ICl _(g) + energy

Label the graph that best represents each of the following stresses and shift.

· adding I_2(g)

· increasing the temperature

· increasing the volume

· removing Cl_2(g)

Worksheet #7 Maximizing Yield

1. N₂O_4(g) + 59 KJ ⇄ 2 NO_2(g)

Describe four ways of increasing the yield of for the reaction above.

Describe three ways to increase the rate of the above reaction.

2. 2SO_3(g) ⇄ 2SO_2(g) + O_2(g) + 215 KJ

Describe four ways of increasing the yield of for the reaction above.

Describe three ways to increase the rate of the above reaction.

3. H₂O_(g) ⇄ H₂O_(l) DH = -150 KJ

Describe three ways of increasing the yield of for the reaction above.

Describe four ways to increase the rate of the above reaction.

4. In the Haber reaction: 3H_2(g) + N_2(g) ⇌ 2NH_3(g) + energy

Explain why each condition is used in the process to make ammonia.

A High pressure of 50 MP

The presence of Ur or Os

Condensing NH₃ to a liquid

A relatively high temperature 500 ^oC

Worksheet #8 Equilibrium Calculations

1. SO_3(g) + H₂O_(g) ⇄ H₂SO_4(l)

At equilibrium [SO₃] = 0.400M [H₂O] = 0.480M [H₂SO₄] = 0.600M

Calculate the value of the equilibrium constant.

2. At equilibrium at 100^oC, a 2.0L flask contains:

0.075 mol of PCl₅ 0.050 mol of H₂O 0.750 mol of HCl 0.500 mol of POCl₃

Calculate the Keq for the reaction:

PCl₅ (s) + H₂O (g) ⇄ 2HCl (g) + POCl₃ (g)

3. Keq= 798 at 25^oC for the reaction: 2SO₂ (g) + O₂ (g) ⇄ 2SO₃ (g).

In a particular mixture at equilibrium, [SO₂]= 4.20 M and [SO₃]=11.0M. Calculate the equilibrium [O₂] in this mixture at 25^oC.

4. Consider the following equilibrium:

2SO₂ (g) + O₂ (g) ⇄ 2SO₃ (g)

0.600 moles of SO₂ and 0.600 moles of O₂ are present in a 4.00 L flask at equilibrium at 100^oC. If the Keq = 680.0, calculate the SO₃ concentration at 100^oC.

5. Consider the following equilibrium: 2 NO_2(g) ⇄ N₂O_4(g)

2.00 moles of NO₂ and1.60 moles of N₂O₄ are present in a 4.00 L flask at equilibrium at 20^oC. Calculate the Keq at 20^oC.

6. 2 SO_3(g) ⇄ 2 SO_2(g) + O_2(g)

4.00 moles of SO₂ and 5.00 moles O₂ are present in a 2.00 L container at 100^oC and are at equilibrium. Calculate the equilibrium concentration of SO₃ and the number of moles SO₃ present if the Keq = 1.47 x 10^-3.

7. If at equilibrium [H₂] = 0.200M and [I₂] = 0.200M and Keq=55.6 at 250^oC, calculate the equilibrium concentration of HI.

H₂ (g) + I₂ (g) ⇄ 2HI (g)

8. 1.60 moles CO, 1.60 moles H₂O, 4.00 moles CO₂, 4.00 moles H₂ are found in an 8.00 L container at 690^oC at equilibrium. CO (g) + H₂O (g) ⇄ CO₂ (g) + H₂ (g)

Calculate the value of the equilibrium constant.

Worksheet #9 Equilibrium Calculations

Solve each problem and show all of your work.

1. At equilibrium, a 5.0L flask contains:

0.75 mol of PCl₅ 0.50 mol of H₂O 7.50 mol of HCl 5.00 mol of POCl₃

Calculate the Keq for the reaction: PCl_{5 (s)} + H₂O _(g) ⇄ 2HCl _(g) + POCl_{3 (g)}

2. Keq= 798 for the reaction: 2SO_{2 (g)} + O_{2 (g)} ⇄ 2SO_{3 (g)}.

In a particular mixture at equilibrium, [SO₂]= 4.20 M and [SO₃]=11.0 M. Calculate the equilibrium [O₂] in this mixture.

3. Consider the following equilibrium: 2SO₂ (g) + O₂ (g) ⇄ 2SO₃ (g)

When 0.600 moles of SO₂ and 0.600 moles of O₂ are placed into a 1.00 litre container and allowed to reach equilibrium, the equilibrium [SO₃] is to be 0.250 M. Calculate the Keq value.

4. Consider the following equilibrium: 2 NO_2(g) ⇄ N₂O_4(g)

2.00 moles of NO₂ are placed in a 1.00 L flask and allowed to react. At equilibrium 1.80 moles NO₂ are present. Calculate the K_eq.

5. 2 SO_2(g) + O_2(g) ⇄ 2 SO_3(g)

4.00 moles of SO₂ and 5.00 moles O₂ are placed in a 2.00 L container at 200^oC and allowed to reach equilibrium. If the equilibrium concentration of O₂ is 2.00 M, calculate the Keq

6. If the initial [H₂] = 0.200 M, [I₂] = 0.200 M and Keq = 55.6 at 250^oC calculate the equilibrium concentrations of all molecules.

H₂ (g) + I₂ (g) ⇄ 2HI (g)

7. 1.60 moles CO and 1.60 moles H₂O are placed in a 2.00 L container at 690 ^oC

(Keq = 10.0). CO (g) + H₂O (g) ⇄ CO₂ (g) + H₂ (g)

Calculate all equilibrium concentrations.

8. SO_3(g) + NO_(g) ⇄ NO_2(g) + SO_2(g)

K_eq = 0.800 at 100^oC. If 4.00 moles of each reactant are placed in a 2.00L container, calculate all equilibrium concentrations at 100^oC.

9. Consider the following equilibrium system: 2NO_2(g) ⇌ N₂O₄

Two sets of equilibrium data are listed for the same temperature.

Container 1 2.00 L 0.12 moles NO₂ 0.16 moles N₂O₄

Container 2 5.00 L 0.26 moles NO₂ ? moles N₂O₄

Determine the number of moles N₂O₄ in the second container. Get a Keq from the first container and use it for the second container.

Worksheet #10 Equilibrium Calculations

Solve each problem and show all of your work in your portfolio.

1. At equilibrium, a 2.0 L flask contains:

0.200 mol of PCl₅ 0.30 mol of H₂O 0.60 mol of HCl 0.300 mol of POCl₃

Calculate the Keq for the reaction:

PCl_{5 (g)} + H₂O _(g) ⇄ 2HCl _(g) + POCl_{3 (g)}

2. Keq= 798 for the reaction: 2SO_{2 (g)} + O_{2 (g)} ⇄ 2SO_{3 (g)}.

In a particular mixture at equilibrium, [SO₂] = 4.20 M and [SO₃] = 11.0M. Calculate the equilibrium [O₂] in this mixture.

3. Consider the following equilibrium: 2SO_{2 (g)} + O_{2 (g)} ⇄ 2SO_{3 (g)}

When a 0.600 moles of SO₂ and 0.600 moles of O₂ are placed into a 2.00 litre container and allowed to reach equilibrium, the equilibrium [SO₃] is to be 0.250 M. Calculate the Keq value.

4. H_2(g) + S_(s) ⇄ H₂S_(g) Keq= 14

0.60 moles of H₂ and 1.4 moles of S are placed into a 2.0L flask and allowed to reach equilibrium. Calculate the [H₂] at equilibrium.

5. Keq = 0.0183 for the reaction: 2HI_(g) ⇄ H_2(g) + I_2(g)

If 3.0 moles of HI are placed in a 5.00L vessel and allowed to reach equilibrium, what is the equilibrium concentration of H₂?

6. Consider the equilibrium: I_{2 (g)} + Cl_{2 (g)} ⇄ 2ICl _(g) Keq= 10.0

The same number of moles of I₂ and Cl₂ are placed in a 1.0L flask and allowed to reach equilibrium. If the equilibrium concentration of ICl is 0.040 M, calculate the initial number of moles of I₂ and Cl₂.

7. Consider the equilibrium: 2ICl_(g) ⇄ I_{2 (g)} + Cl_{2 (g)} Keq= 10.0

If x moles of ICl were placed in a 5.0 L container at 10 ^oC and if an equilibrium concentration of I₂ was found to be 0.60 M, calculate the number of moles ICl initially present.

8. A student places 2.00 moles SO₃ in a 1.00 L flask. At equilibrium [O₂] = 0.10 M at

130 ^oC. Calculate the K_eq. 2SO_2(g) + O_2(g) ⇄ 2SO_3(g)

Worksheet #11 Review, Ktrial, & Size of Keq

1. 2 CrO₄^-2 _(aq) + 2H⁺ _(aq) ⇄ Cr₂O₇^-2 _(aq) + H₂O _(l)

Calculate the Keq if the following amounts were found at equilibrium in a 2.0L volume.

CrO₄^-2 = .030 mol, H⁺ = .020 mol, Cr₂O₇^-2 = 0.32 mol, H₂O = 110 mol

2. PCl_5(s) + H₂O_(g) ⇄ 2HCl _(g) + POCl_{3 (g)} Keq= 11

At equilibrium the 4.0L flask contains the indicated amounts of the three chemicals.

PCl₅ 0.012 mol H₂O 0.016 mol HCl 0.120 mol

Calculate [POCl₃].

3. 6.0 moles H₂S are placed in a 2.0 L container. At equilibrium 5.0 moles H₂ are present. Calculate the Keq 2H₂S_(g) ⇄ 2H_2(g) + S_2(g)

4. 4.0 moles H₂ and 2.0 moles Br₂ are placed in a 1.0L container at 180^oC. If the

[HBr] = 3.0 M at equilibrium, calculate the Keq.

H_2(g) + Br_2(g) ⇄ 2HBr_(g)

5. At 2000 ⁰C Keq = 11.6 for: 2NO_(g) ⇄ N_2(g) + O_2(g). If some NO was placed in a

2.0 L vessel, and the equilibrium [N₂] = 0.120 M, calculate all other equilibrium concentrations.

6. At 800^oC, Keq= 0.279 for CO_2(g) + H_2(g) ⇄ CO_(g) + H₂O_(g).

If 2.00 moles CO_{( g)} and 2.00 moles H₂O _(g) are placed in a 500.0 mL container, calculate all equilibrium concentrations.

7. CO_(g) + H₂O_(g) ⇄ CO_2(g) + H_2(g) Keq= 10.0 at 690^oC. If at a certain time

[CO] = 0.80 M, [H₂O] = 0.050 M, [CO₂] = 0.50 M and [H₂] = 0.40 M, is the reaction at equilibrium? If not, how will it shift in order to get to equilibrium

8. For the reaction: CO_(g) + H₂O_(g) ⇄ CO_2(g) + H_2(g) Keq= 10.0 at 690 ^oC. The following concentrations were observed: [CO]=2.0 M, [H₂]= 1.0 M, [CO₂]=2.0 M, [H₂O] = 0.10 M. Is the reaction at equilibrium? If not, how will it shift in order to get to equilibrium?

9. For the equation below, the following concentrations were observed: [CO] = 1.5 M,

[H₂] = 1.2 M, [CO₂] = 1.0 M, [H₂O] = 0.10 M. Is the reaction at equilibrium? If not, how will it shift in order to get to equilibrium?

CO _(g) + H₂O _(g) ⇄ CO_{2 (g)} + H_{2 (g)} Keq= 10.0 at 690^oC

10. At a certain temperature the Keq for a reaction is 75. 2O_3(g) ⇄ 3O_2(g)

Predict the direction in which the equilibrium will proceed, if any, when the following amounts are introduced to a 10 L vessel.

a) 0.60 mole of O₃ and 3.0 mol of O₂

b) 0.050 mole of O₃ and 7.0 mol of O₂

c) 1.5 mole of O₃ and no O₂

11) Consider the following equilibrium:

a) 2NO_{2 (g)} ⇄ N₂O_{4 (g)} Keq = 2.2

b) Cu²⁺_(aq) + 2Ag_(s) ⇄ Cu_(s) + 2Ag⁺ _(aq) Keq = 1 x 10^-15

c) Pb²⁺ _(aq) + 2 Cl^- (aq) ⇄ PbCl_2(s) Keq = 6.3 x 10⁴

d) SO_2(g) + O_{2 (g)} ⇄ SO_{3 (g)} Keq = 110

i) Which equilibrium favors products to the greatest extent? ______

ii) Which equilibrium favors reactants to the greatest extent? ______

12. What is the only way to change the value of the Keq?

13. In the reaction: A + B ⇄ C + D + 100 kJ, what happens to the value of Keq if we increase the temperature?

14. If the value of Keq decreases when we decrease the temperature, is the reaction exothermic or endothermic?

15. In the reaction; W + X + 100kJ ⇄ Y + Z, what happens to the value of Keq if we increase the (X)? Explain your answer.

16. If the value of Keq increases when we decrease the temperature, is the reaction exothermic or endothermic?

17. Predict whether reactants of products are favored in the following equilibrium systems

(a) CH₃COOH_(aq) ⇄ H⁺_(aq) + CH₃COO^-_(aq) Keq = 1.8 x 10^-5

(b) H₂O_2(aq) ⇄ H⁺_(aq) + HO_2(aq) Keq = 2.6 x 10^-12

(c) CuSO_4(aq) (+ Zn_(s) ⇄ Cu_(s) + ZnSO_4(aq) Keq = 10³⁷

18. What effect will each of the following have on the Keq of the reaction shown below?

2NO_2(g) + heat ⇄ N₂O_4(g) Keq = 2.2

(a) adding a catalyst

(b) increasing the concentration of a reactant

(c) increasing the concentration of a product

(d) decreasing the volume

(e) decreasing the pressure

(f) increasing the temperature

(g) decreasing the temperature

Worksheet #12 Enthalpy & Entropy

For each of these processes, predict if Entropy increases or decreases.

1. 2H_2(g) + O_2(g) ⇄ 2H₂O_(g)

2. 2SO_3(g) ⇄ 2SO_2(g) + O_2(g)

3. Ag⁺_(aq) + Cl^-_(aq) ⇄ AgCl_(s)

4. Cl_2(g) ⇄ 2Cl_(g)

5. H₂O_(l) ⇄ H₂O_(g)

6. CaCO_3(s) + 180 kJ ⇄ CaO_(s) + CO_2(g)

7. I_2(s) + 608 kJ ⇄ I_2(aq)

8. 4Fe_(s) + 3O_2(g) ⇄ 2Fe₂O_3(s) + 1570 kJ

Consider both Enthalpy and Entropy and determine if each reaction will

a) go to completion

b) not occur or

c) go to equilibrium

9. H₂O_(l) ⇄ H₂O_(g) DH = 150 kJ

10. CaCO_3(s) + 180 kJ ⇄ CaO_(s) + CO_2(g)

11. I_2(s) ⇄ I_2(aq) + 608 kJ

12. 4Fe_(s) + 3O_2(g) ⇄ 2Fe₂O_3(s) ∆H = +1570 kJ

13. Cl_2(g) ⇄ 2Cl_(g) DH = +26.8 kJ

14. Ag⁺_(aq) + Cl^-_(aq) ⇄ AgCl_(s) + 86.2 kJ

Consider both Enthalpy and Entropy and determine if each reaction will

a) have a large Keq

b) have a small Keq

c) have a Keq about equal to 1

15. H₂SO_4(aq) + Zn_(s) ⇄ ZnSO_4(aq) + H_2(g) DH = +207 kJ

16. NH₄NO_3(s) ⇄ NH₄⁺_(aq) + NO₃^-_(aq) DH = -30 kJ

17. N_2(g) + 3H_2(g) + 92 kJ ⇄ 2NH_3(g)

18. H₂O_(l) + 150 kJ ⇄ H₂O_(g)

19. Ca_(s) + H₂O_(l) ⇄ Ca(OH)_2(aq) + H_2(g) DH = +210 kJ

Equilibrium Quiz # 1 Approaching Equilibrium

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

A closed container is initially filled with H₂O and CO. As the reaction proceeds towards equilibrium the

A. [CO] and [CO₂] both increase

B. [ CO] and [CO₂] both decrease

C. [CO] increases and [CO₂] decreases

D. [CO] decreases and [CO₂] increases

2. Consider the following equilibrium: 2SO_3(g) ⇄ 2SO_2(g) + O_2(g)

At equilibrium, the rate of decomposition of SO₃

A. Equals the rate of formation of O₂

B. Equals the rate of formation of SO₃

C. Is less than the rate of formation of O₂

D. Is less than the rate of formation of SO₃

3. Which of the following is true for all equilibrium systems?

A. The mass of reactants is equal to the mass of products

B. Addition of a catalyst changes the equilibrium concentrations

C. The concentration of reactants is equal to the concentration of products

D. The rate of the forward reaction is equal to the rate of the reverse reaction

4. Consider the following: 2NH_3(g) ⇄ N_2(g) + 3H_2(g)

A flask is initially filled with NH₃. As the system approaches equilibrium, the rate of the forward reaction

A. Increases as the rate of the reverse reaction decreases

B. Decreases as the rate of the reverse reaction increases

C. Increases as the rate of the reverse reaction increases

D. Decreases as the rate of the reverse reaction decreases

5. A system at equilibrium is said to be dynamic because at equilibrium the

A. Temperature does not change

B. Macroscopic properties are constant

C. Forward and reverse reactions continue to occur

D. Concentrations of reactants and products are constant

6. In all systems at equilibrium, the

A. Concentration of reactants is less than the concentration of products

B. Concentration of reactants and the concentration of products are equal

C. Concentration of reactants is greater than the concentration of products

D. Concentration of reactants and the concentration of products are constant

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

At high temperature, H₂O and CO are placed in a closed container. As the system approaches equilibrium, the

A. Rate of the forward and reverse reaction both increase

B. Rate of the forward and reverse reaction both decrease

C. Rate of the forward reaction decreases and the rate of the reverse reaction increases

D. Rate of the forward reaction increases and the rate of the reverse reaction decreases

8. Which of the following statements are true for all equilibrium systems?

I. Macroscopic Properties are constant

II. Mass of the reactants equals mass of the products

III Equilibrium can be achieved from either products or reactants

A. I and II only

B. I and III only

C. II and III only

D. I, II, and III

9. Consider the following equilibrium: N₂O_4(g) + heat ⇄ 2NO_2(g)

Initially, a 1.0 L container is filled with 2.0 mol of NO₂. As the system approaches equilibrium, the rate of reaction of NO₂

A. Increases and [ N₂O₄ ] increases

B. Increases and [ N₂O₄ ] decreases

C. Decreases and [ N₂O₄ ] increases

D. Decreases and [ N₂O₄ ] decreases

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

Nitrogen gas and oxygen react when placed in a closed container. As the reaction proceeds towards equilibrium, the rate of the reverse reaction

A. Increases as the concentration of products decreases

B. Decreases as the concentration of products decreases

C. Increases as the concentration of products increases

D. Decreases as the concentration of products increases

11. Consider the following

I	Constant Temperature
II	Equal concentrations of reactants and products
III	Equal rates of forward and reverse reactions

A system at equilibrium must have

A. I and II only

B. I and III only

C. II and III only

D. I, II , and III

Equilibrium Quiz #2 LeChatelier’s Principle

1. Consider the following reaction: 2SO_2(g) + O_2(g) ⇄ 2SO_3(g) ∆H = -197 kJ/mol

Which of the following will not shift the equilibrium to the right?

A. Adding more O₂

B. Adding a catalyst

C. Increasing the pressure

D. Lowing the temperature

2. Consider the following equilibrium system: CaCO_3(s) ⇄ CaO_(s) + CO_2(g)

Which one of the following changes would cause the above system to shift left?

A. Add more CaO

B. Remove CaCO₃

C. Decrease volume

D. Increase surface area of CaO

3. Consider the following equilibrium: SO₂Cl_2(g) + energy ⇄ SO_2(g) + Cl_2(g)

When the temperature is decreased, the equilibrium shifts

A. Left and [ SO₂Cl₂ ] increases

B. Left and [ SO₂Cl₂ ] decreases

C. Right and [ SO₂Cl₂ ] increases

D. Right and [ SO₂Cl₂ ] increases

4. Consider the following equilibrium: 2SO_3(g) ⇄ 2SO_2(g) + O_2(g)

The volume of the system is decreased at a constant temperature. A new state of equilibrium is established by a shift of the original equilibrium to the

A. Left and [SO₃] increases

B. Right and [SO₃] decreases

C. Left and [SO₃] remains unchanged

D. Right and [SO₃] remains unchanged

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

Which of the following, when added to the system above, would result in a net decrease in [H₂O]?

A. CO₂

B. H₂

C. CO

D. H₂

6. Consider the following equilibrium: C_(s) + 2H_2(g) ⇄ CH_4(g) + 74 kJ

When a small amount of solid C is added to the system

A. [H₂] decreases

B. [CH₄] increases

C. The temperature increases

D. All concentrations remain constant

7. Consider the following equilibrium: 2NO_(g) + Cl_2(g) ⇄ 2NOCl_(g)

At constant temperature and volume, Cl₂ is added to the above equilibrium system. As equilibrium re-establishes, the

A. [NOCl] will decrease

B. The temperature increases

C. [NO] will increase

D. [NOCl] will increase

8. Consider the following equilibrium: Cl₂O_7(g) +8H_2(g) ⇄ 2HCl_(g) + 7H₂O_(g)

Which of the following would increase the number of moles of HCl?

A. Increase [H₂O]

B. Increase [Cl₂O₇]

C. Increase total pressure

D. Increase volume of the system

9. Consider the following equilibrium: 2HI_(g) ⇄ H_{2(g) +} I_2(g) ∆H = -68kJ

Which of the following would cause the equilibrium to shift right?

A. Increasing the volume

B. Decreasing the volume

C. Increasing the temperature

D. Decreasing the temperature

10. A 1.00 L flask contains a gaseous equilibrium system. The addition of reactants to this flask results in a

A. Shift to the left and decrease in the concentration of products

B. Shift to the left and increase in the concentration of products

C. Shift to the right and decrease in the concentration of products

D. Shift to the right and increase in the concentration of products

11. When the temperature of an equilibrium system is increased, the equilibrium always shifts to favor the

A. Exothermic reaction

B. Endothermic reaction

C. Formation of products

D. Formation of reactants

12. An equilibrium system shifts left when the

A. Rate of the forward reaction is equal to the rate of the reverse reaction

B. Rate of the forward reaction is less than the rate of the reverse reaction

C. Rate of the forward reaction is greater than the rate of the reverse reaction

D. Rate of the forward reaction and the rate of the reverse reaction are constant

13. Consider the following equilibrium: 2SO_2(g) + O_2(g) ⇄ 2SO_3(g) ∆H = -198 kJ

There will be no shift in the equilibrium when

A. More O₂ is added

B. Catalyst is added

C. The volume is increased

D. The temperature is increased

14. Consider the following equilibrium: 2NOCl_(g) ⇄ 2NO_(g) + Cl_2(g)

In a 1.0 L container at equilibrium there are 1.0 mol NOCl, 0.70 mol NO and 0.40 mol Cl₂. At constant temperature and volume, 0.10 mol NOCl is added. The concentrations in the “new” equilibrium in comparison to the concentrations in the “old” equilibrium are

A.

B.

C.

D.

[NOCl]	[NO]	[Cl2]
new = old	new = old	new = old
new > old	new > old	new > old
new < old	new < old	new > old
new < old	new > old	new > old

15. Consider the following equilibrium: N₂O_4(g) + 58 kJ ⇄ 2NO_2(g)

The equilibrium shifts right when

A. NO₂ is added

B. N₂O₄ is removed

C. The temperature is decreased

D. The volume of the system is increased

16. Consider the following equilibrium: 2SO_2(g) + O_2(g) ⇄ 2SO _3(g)

Which of the following will shift the equilibrium to the right?

I. Adding more O₂

II. Adding more SO₃

III. Adding a catalyst

A. I only

B. III only

C. I and II only

D. II and III only

Equilibrium Quiz # 3 Yield/Graphing/LeChatelier’s Principle

1. When a catalyst is added to an equilibrium system, the forward reaction

A. Increases and the reverse decreases

B. Decreases and the reverse decreases

C. Decreases and the reverse increases

D. Increases and the reverse increases

2. Consider the following concentration versus time graph for the equilibrium

N₂O_4(g) ⇄ 2NO_2(g)

“t” TIME(S)

At time= “t”, which one of the following stresses occurred

A. Catalyst was added

B. Pressure was changed

C. Temperature was changed

D. Concentration of NO₂ was changed

3. Which of the following reactions will shift left when pressure is increased and when temperature is decreased?

A. N_2(g) + 2O_2(g) + heat ⇄ 2NO_2(g)

B. N_2(g) + 3H_2(g) ⇄ 2NH_3(g) + heat

C. CH_4(g) + H₂O_(g) + heat ⇄ CO_(g) + 3H_2(g)

D. CS_2(g) + 4H_2(g) ⇄ CH_4(g) + 2H₂S_(g) + heat

4. Consider the following graph, which relates to this equilibrium

N_2(g) + 3H_2(g) ⇄ 2NH_3(g) ∆H = -92kJ

[N₂]

Which of the following caused the changes in the concentrations at time t ?

A. Addition of N₂

B. Removal of H₂

C. Decrease in temperature

D. Decrease in reaction volume

5. Consider the following equilibrium: CH_4(g) + H₂O_(g) + 200kJ ⇄ CO_(g) + 3H_2(g)

In which of the following will both stresses shift the equilibrium right

A. Decrease in temperature and a decrease in volume

B. An increase in temperature and a decrease in volume

C. A decrease in temperature and an increase in volume

D. An increase in temperature and an increase in volume

6. Consider the following equilibrium system: N_2(g) + 3H_2(g) ⇄ 2NH_3(g) + 92 kJ

In order to maximize the yield for this reaction, the best conditions are:

A. Low pressure and low temperature

B. Low pressure and high temperature

C. High temperature and low pressure

D. High pressure and low temperature

7. Consider the following equilibrium system: NH_3(aq) + H₂O_(l) ⇄ NH⁺_4(aq) + OH^--_(aq)

Which of the following when added to the above equilibrium system would cause an increase in [OH^-]

A. NH₃

B. H₂O

C. NH₄⁺

D. HCl

8. Consider the following reversible reaction: Fe³⁺_(aq) + SCN^-_(aq) ⇄ FeSCN²⁺_(aq)

A solution of Fe(NO₃)₃ is added to a solution of KSCN. Which one of the following statements describes the changes in forward and reverse reaction rates as the reaction moves towards equilibrium?

A. Forward and reverse rates increase

B. Forward and reverse rates decrease

C. Forward rate increases and reverse rate decrease

D. Forward rate decreases and reverse rate increase

9. Consider the following equilibrium: N_2(g) + O_2(g) ⇄ 2NO_(g) ∆H= + 181 kJ

When the temperature is decreased, the equilibrium

A. Shifts left and [NO] decreases

B. Shifts left and [NO] increases

C. Shifts right and [NO] increases

D. Shifts right and [NO] decreases

10. Consider the following equilibrium: N_2(g) + 3H_2(g) ⇄ 2NH_3(g) + 92 kJ

In which of the following will both changes shift the equilibrium right?

A. An increase in volume and a decrease in temperature

B. An increase in volume and a increase in temperature

C. A decrease in volume and a decrease in temperature

D. A decrease in volume and an increase in temperature

11. Consider the following equilibrium: CaCO_3(s) + 556 kJ ⇄ CaCO_(s) + CO_2(g)

The equilibrium will shift to the right

A. CaCO₃ is added

B. CO₂ is added

C. The temperature is increased

D. The temperature is decreased

12. Consider the following equilibrium: SO_2(g) + NO_2(g) ⇄ SO_3(g) + NO_(g) + energy

The equilibrium does not shift with a change in the

A. Volume

B. Temperature

C. Concentration of products

D. Concentration of reactants

13. Consider the following equilibrium: 2Hl_(g) ⇄ H_2(g) + I_2(g)

At constant temperature and volume, more I₂ is added to the above equilibrium. A new state of equilibrium results from a shift to the

A. Left with a net decrease in [H₂]

B. Left with a net increase in [H₂]

C. Right with a net increase in [H₂]

D. Right with a net decrease in [H₂]

Quiz #4 Writing and Calculating Keq

1. The equilibrium constant expression for the following reaction is:

2Hg_(l) + O_2(g) ⇄ 2HgO_(s)

A. K_eq = 1/[O₂]

B. K_eq = [O₂]

C. K_eq = [2HgO] / [O₂] [2Hg]

D. Keq = [HgO]² / [Hg]²[O₂]

2. Identify the equilibrium system that least favors the formation of products

A. 2HgO_(s) ⇄ 2Hg_(l) + O_2(g) K_eq = 1.2 x 10^-22

B. CH₃COOH_(aq) + H₂O_(l) ⇄ H₃O⁺_(aq) + CH₃COO^-_(aq) K_eq = 1.8 x 10^-5

C. 2NO_(g) + O_2(g) ⇄ 2NO_2(g) K_eq = 6.5 x 10⁵

D. H_2(g) + Cl_2(g) ⇄ 2HCl_(g) K_eq = 1.8 x 10³³

3. Consider the following equilibrium system: 3O_2(g) ⇄ 2O_3(g) K_eq = 1

Which equation compares the concentration of oxygen and ozone?

A. [O₂] = [O₃]^2/3

B. [O₂] = [O₃]

C. [O₂] = [O₃]^3/2

D. [O₂] ^2/5 = [O₃]

4. For which of the following equilibrium does K_eq = [O₂]

A. O_2(l) ⇄ O_2(g)

B. 2O_3(g) ⇄ 3O_2(g)

C. 2H₂O_(l) ⇄ 2H_2(g) + O_2(g)

D. 2Hg_(s) + O_2(g) ⇄ 2HgO_(s)

5. Consider the following equilibrium system at 25^O C :

2SO_2(g) + O_2(g) ⇄ 2SO_3(g)

At equilibrium, [SO₂] is 4.00 x 10^-3 mol/L, [O₂] = 4.00 x 10^-3 mol/L and

[SO₃] is 2.33 x 10^-3 mol/L. From this data, the K_eq value for the above system is

A. 6.85 x 10^-3

B. 1.18 x 10^-2

C. 84.8

D. 146

6. Consider the following equilibrium system: PCl_5(g) ⇄ PCl_3(g) + Cl_2(g)

At equilibrium, [PCl₅] is a 0.400 M. [PCl₃] is 1.50 M and [Cl₂] is 0.600 M. The K_eq for the reaction is

A. 0.360

B. 0.444

C. 0.900

D. 2.25

7. Consider the following equilibrium: 2H₂S_(g) ⇄ 2H_2(g) + S_2(g)

At equilibrium, [H₂S] = 0.50 mol/L. [H₂] = 0.10 mol/L and [S₂] = 0.40 mol/L.

The value of K_eq is calculated using the ratio

A (0.10)(0.40)

(0.50)

B. (0.10)²(0.40)

(0.50)²

C. (0.50)

(0.10)(0.50)

D. (0.50)²

(0.10)²(0.40)

8. Consider the following equilibrium: 2NO_(g) + Cl_2(g) ⇄ 2NOCl_(g) K_eq = 12

At equilibrium, [NOCl] = 1.60 mol/L and [NO] = 0.80 mol/L. The [Cl₂] is

A. 0.17 mol/L

B. 0.27 mol/L

C. 0.33 mol/L

D. 3.0 mol/L

9. Consider the following equilibrium: I_2(s) + H₂O_(l) ⇄ H⁺_(aq) + I^-_(aq) + HOI_(aq)

The equilibrium constant expression for the above system is

A. K_eq = [H⁺][I^-]

B. K_eq = [H⁺][I^-][HOI]

C. K_eq = [H⁺][I^-][HOI]

[I₂][H₂O]

D. K_eq = [H⁺][I^-][HOI]

[H₂O]

10. Consider the following equilibrium: 2CO_(g) + O_2(g) ⇄ 2CO_2(g)

The ratio used to calculate the equilibrium constant is

A. [2CO]²[O₂]

[2CO₂]²

B. [2CO₂]²

[2CO]²[O₂]

C. [CO]²[O₂]

[CO₂]²

D. [CO₂]²

[CO]²[O₂]

11. Consider the following equilibrium: 2Fe_(s) + 3H₂O_(g) ⇄ Fe₂O_3(s) + 3H_2(g)

The equilibrium constant expression is

A. K_eq = [Fe₂O₃][H₂]³

[Fe]²[H₂O]³

B. K_eq = [Fe₂O₃][3H₂]

[2Fe] [3H₂O]

C. K_eq = [H₂]³

[H₂O]³

D. K_eq = [H₂]³

12. Consider the following equilibrium: N₂O_4(g) ⇄ 2NO_2(g) K_eq = 0.133

At equilibrium, the [N₂O₄] is equal to

A. 0.133

[NO₂]

B. [NO₂]

0.133

C. 0.133

[NO₂]²

D. [NO₂]²

0.133

13. Consider the following equilibrium: 4KO_2(s) + 2H₂O_(g) ⇄ 4KOH_(s) + 3O_2(g)

The equilibrium constant expression is

A. K_eq = [KOH]⁴[O₂]³

[KO₂]⁴[H₂O]²

B. K_eq = [O₂]³

[H₂O]²

C. K_eq = [KO₂]⁴[H₂O]²

[KOH]⁴[O₂]³

D. K_eq = [H₂O]²

[O₂]³

14. Consider the following equilibrium: C_(s) + H₂O_(g) ⇄ CO_(g) + H_2(g)

The contents of a 1.00 L container at equilibrium were analyzed and found to contain 0.20 mol C, 0.20 mol H₂O, 0.60 mol CO and 0.60 mol H₂. The equilibrium constant is

A. 0.11

B. 0.56

C. 1.8

D. 9.0

15. Consider the following equilibrium: N₂O_4(g) ⇄ 2NO_2(g) K_eq = 4.61 x 10^-3

A 1.00 L container at equilibrium was analyzed and found to contain 0.0200 moles NO₂. At equilibrium, the concentration of N₂O₄ is

A. 0.0868 mol/L

B. 0.230 mol/L

C. 4.34 mol/L

D. 11.5 mol/L

16. Consider the following equilibrium: CH_4(g) + H₂O_(g) ⇄ CO_(g) + 3H_2(g) K_eq= 5.7

At equilibrium, the [CH₄] = 0.40 mol/L [CO] = 0.30 mol/L and

[H₂] = 0.80 mol/L. The [H₂O] is

A. 0.067 mol/L

B. 0.11 mol/L

C. 2.2 mol/L

D. 5.3 mol/L

17. Consider the following equilibrium: H_2(g) + I_2(g) ⇄ 2HI_(g)

At equilibrium, the [H₂] = 0.020 mol/L. [I₂] = 0.020 mol/L and [HI] = 0.160 mol/L. The value of the equilibrium constant is

A. 2.5 x 10^-3

B. 1.6 x 10^-2

C. 6.4 x 10¹

D. 4.0 x 10²

18. Consider the following constant expression: K_eq = [CO₂]. Which one of the following equilibrium systems does the above expression represent?

A. CO_2(g) ⇄ CO_2(s)

B. PbO_(s) + CO_2(g) ⇄ PbCO_3(s)

C. CaCO_3(s) ⇄ CaO_(s) + CO_2(g)

D. H₂CO_3(aq) ⇄ H₂O_(l) + CO_2(aq)

19. Given the following equilibrium system: Br_2(g) ⇄ Br_2(l)

The equilibrium constant expression for the above system is

A. K_eq = [Br_2(l)]

[Br_2(g)]

B. K_eq = [Br_2(g)]

C. K_eq = 1 __

[Br_2(g)]

D. K_eq = [Br_2(g)] [Br_2(g)]

 20. Consider the following equilibrium: CO_(g) + 2H_2(g) ⇄ CH₃OH_(g) + 91 kJ

A change in temperature of the above system increases the value of the equilibrium constant. The new state of equilibrium was established by a shift

A. Left as a result of a decrease in temperature

B. Right as a result of a decrease in temperature

C. Left as a result of an increase in temperature

D. Right as a result of an increase in temperature

Equilibrium Quiz # 5 Calculations and Trial Keq

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 equilibrium system at 900^oC: 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 equilibrium system: 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 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

Equilibrium Quiz #6 Enthalpy and Entropy

1. In which of the following reactions does the tendency towards minimum enthalpy and maximum entropy oppose each other?

A. 3O_3(g) ⇄ 2O_2(g) ΔH = +285 KJ

B. 1/2O_2(g) + O_2(g) ⇄ NO_2(g) ΔH = +34 KJ

C. 2H₂O_(g) ⇄ 2H_2(g) + O_2(g) ΔH = +484 KJ

D. P_4(s) + 6H_2(g) ⇄ 4PH_3(g) ΔH = +37 KJ

2. In which of the following systems will the factors of entropy and enthalpy both favour the reactants.

A. 3C_(s) + 3H_2(g) + heat ⇄ C₃H_6(g)

B. PCl_5(g) + heat ⇄ PCl_3(g) + Cl_2(g)

C. NH₄Cl_(s) + heat ⇄ NH₄⁺_(aq) + Cl^-_(aq)

D. Cl_2(g) + 2HI_(g) ⇄ I_2(g) + 2HI_(g) + heat

3. For an exothermic reaction at equilibrium, an increase in temperature will cause the equilibrium to shift

A. left and the K_eq increases

B. left and the K_eq decreases

C. right and the K_eq increases

D. right and the K_eq decreases

4. Consider the equilibrium: COCl_2(g) ⇄ CO_(g) + Cl_2(g) K_eq = 8.1 x 10^-4

For the above system,

A. [COCl₂] < [CO][Cl₂]

B. [COCl₂] = [CO][Cl₂]

C. [COCl₂] > [CO][Cl₂]

D. [COCl₂] = 1/[CO][Cl₂]

5. The value of the equilibrium constant will change when

A. a catalyst is used

B. temperature changes

C. product concentrations change

D. the volume of a gaseous system changes

6. In an exothermic equilibrium reaction involving only gases, the value of the Keq can be decreased by

A. adding some reactant gas

B. removing some reactant gas

C. increasing the temperature

D. decreasing the temperature

7. Consider the equilibrium: H_2(g) + CO_2(g) ⇄ CO_(g) + H₂O_(g) ΔH = +41KJ

The temperature of the above equilibrium system is increased while kept at a constant volume. A new state of equilibrium is established in which there is

A. an increase in [CO] and a decrease in K_eq

B. an increase in [CO] and a increase in K_eq

C. an increase in [CO₂] and a decrease in K_eq

D. an increase in [CO₂] and a increase in K_eq

8. Consider the following equilibrium: 2NO_2(g) ⇄ N₂O_4(g) + 59KJ

For the above reaction,

A. both minimum enthalpy and maximum entropy favour the products.

B. both minimum enthalpy and maximum entropy favour the reactants.

C. minimum enthalpy favours reactants and maximum entropy favours products.

D. minimum enthalpy favours products and maximum entropy favours reactants.

9. In which of the following does entropy decrease?

A. NaCl_(s) → Na⁺_(aq) + Cl^-_(aq)

B. 4NO_(g) + 6H₂O_(g) → 4NH_3(g) + 5O_2(g)

C. 2NaCHCO_3(s) → Na₂CO_3(s) + CO_2(g) + H2O_(g)

D. CaCO_3(s) + HCl_(aq) → CaCl_2(aq) + CO_2(g) + H₂O_(l)

10. Consider the following possible reaction: N₂O_(g) + NO_2(g) → 3NO_(g) + heat

Which of the following statements is correct?

A. Minimum enthalpy and maximum entropy both favour the products.

B. Minimum enthalpy and maximum entropy both favour the reactants.

C. Minimum enthalpy favours the reactants and maximum entropy favours the products.

D. Minimum enthalpy favours the products and maximum entropy favours the reactants.

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

At equilibrium in a 1.0L container, there are 3.0 mol COCl₂, 0.49 mol CO, and 0.49 mol Cl₂. At constant temperature the volume of the above system is decreased to 0.50L. When equilibrium is reestablished the

A. concentrations of all three gases have increased

B. concentrations of all three gases have decreased

C. [COCl₂] has increased and [CO] and [Cl₂] have decreased

D. [COCl₂] has decreased and [CO] and [Cl₂] have increased

12. Chemical systems move toward positions of

A. minimum enthalpy and maximum entropy

B. maximum enthalpy and minimum entropy

C. constant enthalpy and constant entropy

D. maximum enthalpy and maximum entropy

13. Hydrogen gas dissociates into atomic hydrogen as follows:

H_2(g) ⇄ 2H_(g) Keq = 1.2 x 10^-71

The value of the equilibrium constant for the above system indicates that

A. the reaction rate is very slow

B. the equilibrium is exothermic

C. reactants are favoured in this equilibrium

D. a catalyst is necessary to establish equilibrium

14. Consider the following reaction:

Na₂CO_3(s) + HCl_(aq) ⇄ 2NaCl_(aq) + CO_2(g) + H₂O_(l) ΔH = -27.7 KJ

In this reaction,

A. Minimum enthalpy and maximum entropy both favour the products.

B. Minimum enthalpy and maximum entropy both favour the reactants.

C. Minimum enthalpy favours the products and maximum entropy favours the reactants.

D. Minimum enthalpy favours the reactants and maximum entropy favours the products.

15. In an endothermic equilibrium system, the

A. Minimum enthalpy and maximum entropy both favour the products.

B. Minimum enthalpy and maximum entropy both favour the reactants.

C. Minimum enthalpy favours the products and maximum entropy favours the reactants.

D. Minimum enthalpy favours the reactants and maximum entropy favours the products.

Web Review

1. Describe the changes in reactant and product concentration as equilibrium is approached.

2. Describe the changes in the forward and the reverse rates as equilibrium is approached.

3. State three conditions that are necessary to achieve equilibrium.

4. Assuming all three conditions are present, describe what would happen if only reactants are placed in a container.

5. Assuming all three conditions are present, describe what would happen if only

products are placed in a container.

6. Describe the relationship between the size of the equilibrium constant, large, small, or about 1, and the relative amounts of reactants or products.

7. Describe each of the following:

Dynamic equilibrium,

LeChatelier's principle,

Ktrial,

Enthalpy,

Entropy

Macroscopic property.

8. Describe the effect of temperature on the equilibrium constant for an exothermic and endothermic reaction.

9. Describe the effect of changing the temperature, pressure , volume, concentration or adding a catalyst on the value of the equilibrium constant.

10. What is the only variable that will change the value of the equilibrium constant.

11. What are the phases of the compounds that are not included in the equilibrium expression.

12. Write the equilibrium expression for: 4A_(g) + 3B_(aq) ⇄ 2C_(l) + 3D_(s)

13. Pick the best Keq for each of the reactions. Keq = 100 Keq = 0.01 Keq = 1.0

a) Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g) + 152kJ

b) 3C_(s) + 3H_2(g) ⇄ C₃H_6(g) ΔH = +20.4 kJ

c) 2Pb(NO₃)_2(s) + 597 kJ ⇄ 2PbO_(s) +4NO_2(g) + O_2(aq)

14. For each reaction in equilibrium describe the shift for the following changes: increasing temperature, increasing pressure, decreasing volume, adding a gaseous product and removing an aqueous reactant.

a) Zn_(s) + 2HCl_(aq) ⇄ ZnCl_2(aq) + H_2(g) + 152kJ

b) A_(aq) + 6B_(g) ⇄ 2C_(g) + 4D_(g) ΔH= +56kJ

15. Zn_(s) + 2HCl_(aq) ⇄ ZnCl_2(aq) + H_2(g) + 152kJ

Give three ways to increase the yield of the reaction.

Give five ways to increase the rate of the reaction.

16. A_(aq) + 6B_(g) ⇄ 2C_(g) + 2D_(g) ΔH= +56kJ

Give three ways to increase the yield of the reaction.

Give five ways to increase the rate of the reaction.

17. What is equal at equilibrium?

18. What is constant at equilibrium?

19. Which reaction has the greatest yield? Why?

a) Keq = 8.0 x 10^-12 b) Keq = 7.0 x 10^-11

20. Which reaction has the smallest yield?

a) Keq = 1.0 x 10^-15 b) Keq = 9.0 x 10^-15

21. Which has the greater entropy?

a) H₂O_(s) b) H₂O_(l) c) H₂O_(g)

22. Which has the greater enthalpy?

a) H₂O_(s) b) H₂O_(l) c) H₂O_(g)

Hint: Consider H₂O_(s) → H₂O_(l) Draw a potential energy diagram. Which side is higher?

23. Review your kinetics test. There will be 5 questions on this test from kinetics.

24. Consider the following equilibrium system: SO_3(g) + NO_(g)⇄NO_2(g) + SO_2(g)

a) Describe what happens to the forward and reverse reaction rate immediately after adding SO_3(g)

b) Describe what happens to the forward and reverse reaction rate immediately after removing NO_2(g)

c) Describe what happens to the forward and reverse reaction rate immediately after adding a catalyst .

d) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after removing NO_2(g)

e) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after adding SO_3(g)

f) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after adding a catalyst .

g) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after decreasing the volume of the container.

h) Describe what happens to the reactant and product concentrations after a new equilibrium has formed compared to the original equilibrium after decreasing the volume of the container.

Part 2 Calculations

1. SO_3(g) + NO_(g) ⇄ NO_2(g) + SO_2(g) [SO₃] = 0.400M [NO] = 0.480M

[NO₂] = 0.600M [SO₂] = 0.450M Keq = 0.800 at 100ºC

a) Show by calculation that this reaction mixture is not at equilibrium at 100ºC.

b) What will happen to [SO₃] and [SO₂] as the system moves to equilibrium?

2. Consider the equilibrium below:

Co(H₂O)₆⁺²_(aq) + 2Cl^-1_(aq) ⇄ Co(H₂O)₆Cl_2(aq) + 2H₂O_(l)

pink blue

If the colour of the equilibrium mixture is pink at 5ºC and blue at 60ºC, is the reaction endothermic or exothermic?

3. SO_3(g) + H₂O_(g) ⇄ H₂SO_4(l)

[SO₃] = 0.400M [H₂O] = 0.480M [H₂SO₄] = 0.600M

Calculate the value of the equilibrium constant.

4. 2SO_2(g) + O_2(g) ⇄ 2SO_3(g)

4.00 moles of SO₂ and 5.00 moles O₂ are placed in a 2.00 L container at 200ºC and allowed to reach equilibrium. If the equilibrium concentration of O₂ is 2.00M, calculate the Keq.

5. 2SO_2(g) + O_2(g) ⇄ 2SO_3(g)

If at equilibrium [O₂] = 0.500M and [SO₃] = 0.400M and the equilibrium constant is the same as question 4 at 200ºC, calculate the [SO₂].

6. Consider the following equilibrium:

2NO_2(g) ⇄ N₂O_4(g)

2.00 moles of NO₂ are placed in a 1.00 L flask and allowed to react. At equilibrium 1.80M NO₂ are present. Calculate the Keq.

7. SO_3(g) + NO_(g) ⇄ NO_2(g) + SO_2(g) Keq = 0.800 at 100ºC

If 4.00 moles of each reactant is placed in a 2.00L container, calculate all equilibrium concentrations at 100ºC.

8. Keq = 0.0183 at 150ºC for: 2HI(g) ⇄ H_2(g) + I_2(g)

If 3.00 moles of HI is placed in a 5.00 L container and allowed to establish equilibrium, what are all equilibrium concentrations?

Challenge Question

9. Consider the following equilibrium in a 5.00 L container:

CO _(g) + H₂O _(g) ⇄ CO_2(g) + H_{2 (g)}

At equilibrium, there is 1.0 mole of CO, 3.0 moles of H₂O, 3.0 moles CO₂, and 3.0 moles of H₂. If 2.0 moles of CO are now added, find the equilibrium [CO₂].

Hint: first calculate the Keq, then do an ICE chart with the initial concentrations after CO is added.

Equilibrium Practice Test # 1

1. Consider the following reaction mechanism:

Step1: NO_(g) + O_3(g) → NO_2(g) + O_2(g)

Step2: O_(g) + NO_2(g) → NO_(g) + O_2(g)

The catalyst is:

A. O₂

B. O₃

C. NO

D. NO₂

2. Consider the following reaction: 2NH_3(g) ⇄ N_2(g) + 3H_2(g)

A flask is initially filled with NH₃. As the system approaches equilibrium, the rate of the forward reaction

A. increases as the rate of the reverse reaction decreases

B. decreases as the rate of the reverse reaction increases

C. increases as the rate of the reverse reaction increases

D. decreases as the rate of the reverse reaction decreases

3. Consider the following reaction:

Na₂CO_3(s) + 2HCl_(aq) → 2NaCl_(aq) + CO_2(g) + H₂O_(l) ΔH = -153 KJ

In this reaction

A. minimum enthalpy and maximum entropy both favour the products

B. minimum enthalpy and maximum entropy both favour the reactants

C. minimum enthalpy favours products and maximum entropy reactants

D. minimum enthalpy favours reactants and maximum entropy products

4. In all systems at equilibrium, the

A. concentration of reactants is less than the concentration of the products

B. concentration of reactants and the concentration of the products are equal

C. concentration of reactants is greater than the concentration of the products

D. concentration of reactants and the products are constant

5. Consider the following mechanism: Step 1: N₂O_(g) → N_2(g) + O_(g)

Step 2: N₂O(g) + O_(g) → N_2(g) + O_2(g)

A reactant in the overall equation is

A. O

B. O₂

C. N₂

D. N₂O

6. Chemical systems tend to move toward positions of

A. minimum enthalpy and maximum entropy.

B. maximum enthalpy and minimum entropy.

C. minimum enthalpy and minimum entropy.

D. maximum enthalpy and maximum entropy.

7. An equilibrium system shifts left when the

A. rate of the forward reaction is equal to the rate of the reverse reaction.

B. rate of the forward reaction is less than the rate of the reverse reaction.

C. rate of the forward reaction is greater than the rate of the reverse reaction.

D. rate of the forward reaction and the reverse reaction are constant.

8. A 1.00 L flask contains a gaseous equilibrium system. The addition of reactants to this flask results in a

A. shift left and a decrease in the concentration of the products.

B. shift left and a increase in the concentration of the products.

C. shift right and a decrease in the concentration of the products.

D. shift right and a increase in the concentration of the products.

9. Consider the following equilibrium: CH_4(g) + H₂O_(g) + heat ⇄ CO_(g) + 3H_2(g)

In which of the following will both stresses shift the equilibrium to the right?

A. a decrease in temperature and a decrease in volume

B. a increase in temperature and a decrease in volume

C. a decrease in temperature and a increase in volume

D. a increase in temperature and a increase in volume

10. Consider the following equilibrium: 2SO_2(g) + O_2(g) ⇄ 2SO_3(g) ∆H = -198 kJ

There will be no shift in this equilibrium when

A. more O₂ is added.

B. a catalyst is added.

C. the volume is increased.

D. the temperature is increased.

11. Consider the following equilibrium: 2Fe_(s) + 3H₂O_(g) ⇄ Fe₂O_3(s) + 3H_2(g)

The equilibrium expression is

A. Keq = [Fe₂O₃][H₂]³ B. Keq = [Fe₂O₃][3H₂]

[Fe]²[H₂O]³ [2Fe][3H₂O]

C. Keq = [H₂]³ D. Keq = [ H₂]³

[H₂O]³

12. Consider the following equilibrium: N₂O_4(g) ⇄ 2NO_2(g) Keq = 0.133

At equilibrium, the [N₂O₄] is equal to

A. 0.133 B. [NO₂]

[NO₂] 0.133

C. 0.133 D. [NO₂]²

[NO₂]² 0.133

13. Which of the following equilibrium systems most favours 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^-7

14. Consider the following equilibrium: 4KO_2(s) + 2H₂O_(g) ⇄ 4KOH_(s) + 3O_2(g)

The equilibrium expression is

A. Keq = [KOH]⁴[O₂]³ B. Keq = [O₂]³

[KO₂]²[H₂O]² [ H₂O]²

C. Keq = [KO₂]⁴[H₂O]² D. Keq = [ H₂O]²

[KOH]⁴[O₂]³ [O₂]³

15. Consider the following equilibrium: N_2(g) + O_2(g) ⇄ 2NO_(g) ∆H = +181 kJ

When the temperature is decreased, the equilibrium:

A. shifts left and the Keq value increases

B. shifts left and the Keq value decreases

C. shifts right and the Keq value increases

D. shifts right and the Keq value decreases

16. Consider the following equilibrium: CaCO_3(s) + 556 kJ ⇄ CaO + CO_2(g)

The value of the equilibrium constant will increase when

A. CO₂ is added.

B. CO₂ is removed.

C. the temperature is increased.

D. the temperature is decreased.

17. Consider the following equilibrium: C_(s) + H₂O_(g) ⇄ CO_(g) + H_2(g)

The contents of a 1.00 L container at equilibrium were analyzed and found to contain 0.20 mole C, 0.20 mole H₂O, 0.60 mole CO, and 0.60 mole H₂, The equilibrium constant is

A. 0.11

B. 0.56

C. 1.8

D. 0.0

18. Consider the following equilibrium: N₂O_4(g) ⇄ 2NO_2(g) Keq = 4.61 x 10^-3

A 1.00 L container at equilibrium was analyzed and found to contain

0.0200 mole NO₂. At equilibrium, the concentration of N₂O₄ is

A. 0.0868 M

B. 0.230 M

C. 4.34 M

D. 11.5 M

19. Consider the following potential energy diagram:

The forward reaction is

A. exothermic and the ∆H = -50 kJ

B. endothermic and the ∆H = +50 kJ

C. exothermic and the ∆H = -225 kJ

D. endothermic and the ∆H = +225 kJ

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

A closed container is initially filled with H2O and CO. As the reaction proceeds to equilibrium the

A. [CO] and [CO₂] both increase

B. [CO] and [CO₂] both decrease

C. [CO] increases and [CO₂] decreases

D. [CO] decreases and [CO₂] increases

21. Consider the equilibrium: H_2(g) + I_2(g) ⇄ 2HI_(g) The pressure of the system is increased by reducing the volume. When comparing the new equilibrium with the original equilibrium,

A. all concentrations remain constant

B. the concentrations of all species have increased

C. reactant concentrations have increased while products decreased

D. reactant concentrations have decreased while products increased

22. Consider the following equilibrium: N₂O_4(g) ⇄ 2NO_2(g) A 1.00 L container is initially filled with 0.200 moles of N₂O₄. At equilibrium, 0.160 moles NO₂ are present. What is the equilibrium concentration of N₂O₄?

A. 0.040 M

B. 0.080 M

C. 0.120 M

D. 0.160 M

23. Equilibrium is dynamic process because the

A. macroscopic properties are not changing

B. mass of the reactants equals the mass of the products

C. forward and reverse reactions continue to occur

D. concentrations of reactants and products are constant

24. Consider the following equilibrium: C_(s) + 2H_2(g) ⇄ CH_4(g) The addition of H2 will cause the equilibrium to shift to the

A. left and [CH₄] will increase

B. left and [CH₄] will decrease

C. right and [CH₄] will increase

D. right and [CH₄] will decrease

25. Given the following system: 2CrO₄^2-_(aq) + 2H⁺_(aq) ⇄ Cr₂O₇^2-_(aq) + H₂O_(l) Which of the following chemicals, when added to the above equilibrium, would result in a decrease in [CrO₄^2-]?

A. NaOH

B. HNO₃

C. Na₂CrO₄

D. Na₂Cr₂O₇

26. Addition of a catalyst to an equilibrium system

A. increases the value of the Keq.

B. increases the yield of the products.

C. has no effect on the rates of the reaction.

D. increases the rate of formation of both reactants and products.

27. Consider the following reaction: 2B_(s) + 3F_2(g) ⇄ 2BF_3(g) The equilibrium expression is

A. Keq = [2BF₃]

[3F₂]

B. Keq = [F₂]³

[BF₃]

C. Keq = [BF₃]²

[F₂]³

D. Keq = [BF₃]²

[B][F₂]³

28. Consider the following equilibrium: 2NO_(g) ⇄ N_2(g) + O_2(g) Keq = 2.01 x 10³⁰

The value of the equilibrium constant indicates that the

A. [NO]² < [N₂][ O₂]

B. [NO]² > [N₂][ O₂]

C. [NO] = [N₂][ O₂]

D. [NO] > [N₂][ O₂]

29. Consider the equilibrium: H_2(g) + I_2(g) ⇄ 2HI_(g)

At equilibrium the [H₂} = 0.020 M, [I₂] = 0.020 M, and [HI] = 0.160 M. The value of the equilibrium constant is:

A. 2.5 x 10^-3

B. 1.6 x 10^-2

C. 6.4 x 10¹

D. 4.0 x 10²

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

A 1.0 L flask contains a mixture of 1.8 x 10^-1 mole H₂O, 4.0 x 10^-4 mole Cl₂O, and 8.0 x 10^-2 mole HOCl. To establish equilibrium, the system will proceed to the

A. left because the trial Keq > Keq

B. left because the trial Keq < Keq

C. right because the trial Keq > Keq

D. right because the trial Keq < Keq

31. Consider the following equilibrium: SO_2(g) + NO_2(g) ⇄ SO_3(g) + NO + energy

The equilibrium does not shift with a change in

A. volume

B. temperature

C. concentration of products

D. concentration of reactions

32. Consider the following equilibrium : SO₂Cl_2(g) + energy ⇄ SO_2(g) + Cl_2(g)

When the temperature is decreased, the equilibrium shifts

A. left and the [SO₂Cl₂] increases

B. left and the [SO₂Cl₂] decreases

C. right and the [SO₂Cl₂] increases

D. right and the [SO₂Cl₂] decreases

33. Consider the following equilibrium: NH_3(g) + HCl_(g) ⇄ NH₄Cl_(s) + energy

Which of the following will result in a decrease in the mass of NH₄Cl?

A. adding NH₃

B. removing HCl

C. decreasing the volume

D. decreasing the temperature

34. Consider the following equilibrium: PCl_3(g) + Cl_2(g) ⇄ PCl_5(g)

When 0.40 moles of PCl₃ and 0.40 moles of Cl₂ are placed in a 1.00 L container and allowed to reach equilibrium, 0.244 mole of PCl₅ are present. From this information, the value of the Keq is

A. 0.10

B. 0.30

C. 3.3

D. 10

Subjective

1. Concentrations of H₂, I₂, and HI in a mixture at equilibrium at 425 ^oC were found to be 1.52 x 10^-2 M, 3.55 x 10^-2 M, and 2.57 x 10^-1 M respectively. Calculate the equilibrium constant.

H_2(g) + I_2(g) ⇄ 2HI_(g)

2. 4.00 moles of PCl₅ are placed in a 2.00 L container and goes to equilibrium at

200 ^oC. If 0.60 moles of PCl₅ are present at equilibrium, calculate the equilibrium constant.

PCl_5(g) ⇄ PCl_3(g) + Cl_2(g)

3. An equilibrium system has a Keq = 50 at 0 ^oC and a Keq = 80 at 20 ^oC.

a) As the temperature was increased, which direction did the reaction shift?

b) Is the reaction endothermic or exothermic?

4. If the initial [H₂] = 0.200 M and [I₂] = 0.200 M and the Keq = 55.6 at 20 ^oC, calculate the equilibrium concentration of all molecules.

H_2(g) + I_2(g) ⇄ 2HI_(g)

5. Consider the following data obtained for the following equilibrium:

Fe³⁺_(aq) + SCN^-_(aq) ⇄ FeSCN²⁺_(aq)

[Fe³⁺] [SCN^-] [FeSCN²⁺]

Experiment 1 3.91 x 10^-2 M 8.02 x 10^-5 M 9.22 x 10^-4 M

Experiment 2 6.27 x 10^-3 M 3.65 x 10^-4 M ?

Calculate [FeSCN²⁺] in experiment 2.

6. 1.60 moles CO, 1.60 moles H₂O, 6.00 moles CO₂, and 6.00 moles H₂ are put in a

2.00 L container at 600 ^oC.

CO(g) + H₂O(g) ⇄ CO_2(g) + H_2(g) Keq = 10.0

a) Show by calculation the reaction is not at equilibrium.

b) Which way will the reaction shift in order to achieve equilibrium?

c) Calculate the equilibrium concentration of CO₂.

Equilibrium Practice Test # 2

1. The slowest of the following reactions is:

A. Ag⁺_(aq) + Cl^-_(aq) → AgCl_(s)

B. H⁺_(aq) + OH^-_(aq) → 2H₂O_(l)

C. 3Ba²⁺_(aq) + 2PO₄^3-_(aq) → Ba₃(PO₄)_2(aq)

D. Cu_(s) + 2Ag⁺_(aq) → Cu²⁺_(aq) + 2Ag_(s)

2. The rate of a chemical reaction is equal to the slope of the line with axes labelled

x-axis y-axis

A. time rate

B. mass time

C. volume of gas time

D. time concentration

3. Consider the following reaction: CH_4(g) + 2O_2(g) → CO_2(g) + 2H₂O_(g) + heat

The diagram that represents the relationship between rate and temperature is:

4. Which of the following describes the energy of colliding particles as reacting molecules approach each other?

KE PE

A. decreases increases

B. increases decreases

C. decreases remains constant

D. remains constant increases

5. The average kinetic energy per molecule can be increased by

A. adding a catalyst

B. increasing pressure

C. increasing temperature

D. increasing reactant concentration

6. Consider the following reaction: C_(s) + 2H_2(g) ⇄ CH_4(g) ΔH = -74.8 kJ

Which of the following will cause an increase in the value of the Keq?

A. increasing [H₂]

B. decreasing the volume

C. finely powdering the C_(s)

D. decreasing the temperature

7. Consider the following equilibrium: H_2(g) + I_2(g) ⇄ 2HI_(g)

At equilibrium [H₂] = 0.00220 M, [I₂] = 0.00220 M, and [HI] = 0.0156 M

The value of the Keq is

A. 3.10 x 10^-4

B. 1.99 x 10^-2

C. 5.03 x 10¹

D. 3.22 x 10³

8. Consider the rate diagram for the following reaction: 2HI_(g) ⇄ H_2(g) + I_2(g)

Which of the following occurs at t₁?

A. addition of H₂

B. addition of HI

C. addition of a catalyst

D. a decrease in volume

9. Chemical equilibrium is said to be dynamic because

A. the reaction proceeds quickly

B. the mass of the reactants is decreasing

C. the macroscopic properties are constant

D. both forward and reverse rates are occurring

10. Which equation has the largest value of Keq?

A. N_2(g) + O_2(g) ⇄ 2NO_(g) ΔH = 21 kJ

B. C₂H_6(g) ⇄ 2C_(s) + 3H_2(g) ΔH + 83 kJ

C. H_2(g) + 1/2O_2(g) ⇄ H₂O_(g) ΔH = -240 kJ

D. Ca_(s) + 3H₂O_(l) ⇄ Ca(OH)_2(aq) + H_2(g) ΔH = -240 kJ

11. The value of the Keq can be changed by

A. adding a catalyst

B. changing the temperature

C. changing the reactant concentration

D. changing the volume of the container

12. Consider the following equilibrium: PCl_3(g) + Cl_2(g) ⇄ PCl_5(g)

When 0.40 mole of PCl₃ and 0.40 mole of Cl₂ are placed in a 1.00 L container and allowed to reach equilibrium, 0.244 mole of PCl₅ are present. From this information, the value of the Keq is

A, 0.10

B. 0.30

C. 3.3

D. 10

13. Consider the following equilibrium: PCl_3(g) + Cl_2(g) ⇄ PCl_5(g) Keq = 2.30

A 1.0 L container is filled with 0.05 mole PCl₅, 1.0 mole PCl₃, and 1.0 mole Cl₂. The system proceeds to the

A. left because the Trial Keq > Keq

B. left because the Trial Keq < Keq

C. right because the Trial Keq > Keq

D. right because the Trial Keq < Keq

14. Given the following system: 2CrO₄^2-_(aq) + 2H⁺_(aq) ⇄ Cr₂O₇^2-_(aq) + H₂O_(l)

Which of the following chemicals, when added to the above system at equilibrium, would result in a decrease in [Cr₂O₇^2-]?

A. NaOH

B. HNO₃

C. Na₂CrO₄

D. Na₂Cr₂O₇

15. What is the Keq expression for the following equilibrium?

3Fe_(s) + 4H₂O_(g) ⇄ Fe₃O_4(s) + 4H_2(g)

A. Keq = [H₂]⁴

B. Keq = [H₂]

[H₂O]

C. Keq = [H₂]⁴

[H₂O]⁴

D. Keq = [Fe₂O₃][H₂]⁴

[Fe][H₂O]⁴

16. Consider the following equilibrium: 2O_3(g) ⇄ 3O_2(g) Keq = 65

Initially 0.10 mole of O₃ and 0.10 mole of O₂ are placed in a 1.0 L container, Which of the following describes the changes in concentrations as the reaction proceeds towards equilibrium?

[O₃] [O₂]

A. decreases decreases

B. decreases increases

C. increases decreases

D. increases increases

17. Consider the following equilibrium: 2CrO₄^2-_(aq) + 2H⁺_(aq) ⇄ Cr₂O₇^2-_(aq) + H₂O_(l)

yellow orange

An unknown solution is added to an orange equilibrium system until the sample turns yellow. The solution could be

A. KNO₃

B. NaOH

C. NH₄NO₃

D. CH₃COOH

18. Consider the following equilibrium:

CH₃COOH_(aq) ⇄ CH₃COO^-_(aq) + H⁺_(aq) + heat

A stress was applied at time t₁ and the data plotted on the following graph:

The stress imposed at time t₁ is the result of

A. the addition of HCl

B. decreasing the temperature

C. the addition of NaCH₃COO

D. increasing the volume of the container

19. Consider the following potential energy diagram for an equilibrium system:

When the temperature of the system is increased, the equilibrium shifts to the

A. left and the Keq increases

B. left and the Keq decreases

C. right and the Keq increases

D. right and the Keq decreases

20. Addition of a catalyst to an equilibrium system

A. increases the value of the Keq

B. increases the yield of the product

C. has no effect on the rates of the reaction

D. increases the rates of formation of both reactants and products

21. Ammonia, NH₃, is produced by the following reaction:

N_2(g) + 3H_2(g) D 2NH_3(g) + energy

Which of the following would result in the highest concentration of ammonia at equilibrium?

A. increasing the temperature and increasing the pressure

B. decreasing the temperature and increasing the pressure

C. increasing the temperature and decreasing the pressure

D. decreasing the temperature and decreasing the pressure

22. Consider the following equilibrium:

2NO_2(g) D N₂O_4(g) K_eq = 1.15

The equilibrium concentration of NO₂ is 0.50 mol/L. Calculate the equilibrium concentration of N₂O_4(g).

A. 0.22 mol/L

B. 0.29 mol/L

C. 0.43 mol/L

D. 0.58 mol/L

23. Consider the following equilibrium:

H_2(g) + I₂ D 2HI_(g) K_eq = 50.0

What is the value K_eq for the reaction rewritten as:

2HI_(g) D H_2(g) + I_2(g) K_eq = ?

A. -50.0

B. 0.0200

C. 25.0

D. 50.0

24. Consider the following equilibrium: 2NOCl_(g) D 2NO_(g) + Cl_2(g)

A flask is filled with NOCl, NO, and Cl_2(g). Initially there were a total of 5.0 moles of gases present. When equilibrium is reached, there are a total of 8.0 moles of gases present. Which of the following explains the observation?

A. The reaction shifted left because the Trial Keq > Keq

B. The reaction shifted left because the Trial Keq < Keq

C. The reaction shifted right because the Trial Keq > Keq

D. The reaction shifted right because the Trial Keq < Keq

25. Consider the following equilibrium:

4NH_3(g) + 5O_2(g) D 4NO_(g) + 6H₂O_(g) + energy

Which of the following will cause the equilibrium to shift to the left?

A. adding H₂O_(g)

B. removing some NO_(g)

C. increasing the volume

D. decreasing the temperature

26. A catalyst is added to a system already at equilibrium. How are the forward and reverse reaction rates affected by the addition of the catalyst.

Forward Rate Reverse Rate

A. increases increases

B. increases constant

C. constant decreases

D. constant constant

27. Consider the following equilibrium: 2NOBr_(g) D 2NO_(g) + Br_2(g) Keq = 0.064

At equilibrium, a 1.00 L flask contains 0.030 mole NOBr and 0.030 mole NO. How many moles of Br₂ are present?

A. 0.0019

B. 0.064

C. 0.030

D. 0.47

28. Which of the following does not apply to all chemical equilibrium systems?

A. They are closed.

B. The macroscopic properties are constant

C. Forward and reverse rates are equal

D. There are equal concentrations of reactants and products

29. The relationship between Ea and reaction rate is best represented as

30. The relationship between Keq and temperature for an exothermic reaction is best represented as

31. The relationship between reaction rate and temperature is best represented by

32. The relationship between Ea and temperature is best represented by

32. Methanol, CH₃OH, can be produced by the following:

CO_(g) + 2H_2(g) D CH₃OH_(g) + energy

The conditions necessary to maximize the equilibrium yield of CH₃OH are

A. low temperature and low pressure

B. high temperature and low pressure

C. low temperature and high pressure

D. high temperature and high pressure

33. Consider the following equilibrium: 2NO_(g) + O_2(g) D 2NO_2(g) + energy

When the volume of the container is increased, the equilibrium shifts to the

A. left and the Keq decreases

B. right and the Keq increases

C. left and the Keq remains constant

D. right and the Keq remains comstant

34. Consider the following reaction:

C₃H_8(g) + 5O_2(g) Š 3CO_2(g) + 4H₂O_(g) ΔH = -2202 kJ

Which of the following applies to the forward reaction?

Entropy Enthalpy

A. increases increases

B. increases decreases

C. decreases increases

D. decreases decreases

Subjective

1. Consider the following equilibrium:

N₂H_4(g) + 2O_2(g) D 2NO_2(g) + 2H₂O_(g)

More oxygen is added to the above equilibrium. After the system re-establishes equilibrium, identify the substance(s), if any, that have a net

a) increase in concentration

b) decrease in concentration

2. Given the following equilibrium: H_2(g) + I_2(g) D 2HI_(g)

Initially, 0.200 mole H₂ and 0.200 mole I₂ were placed into a 1.0 L container. At equilibrium, the [I₂] is 0.040 M. Calculate the Keq.

3. Consider the following equilibrium: 2CrO₄^2-_(aq) + 2H⁺_(aq) ⇄ Cr₂O₇^2-_(aq) + H₂O_(l)

yellow orange

When HCl is added, the solution turns orange. Explain why this colour change occurs.

4. Consider the following equilibrium system:

N_2(g) + 3H_2(g) D 2NH_3(g) + energy

A 1.00 L container is filled with 7.0 mole NH₃ and the system proceeds to equilibrium as indicated by the graph.

a) Draw and label the graph for N₂ and H₂. Fill in an ICE chart if you are not sure how to do this.

N_2(g) + 3H_2(g) D 2NH_3(g)

I

C

E

b) Calculate the Keq for the above reaction.

5. Consider the following equilibrium 2NO_(g) + O_2(g) D 2NO_2(g) Keq = 1.5

0.800 mole NO, 0.600 moles O₂, and 0.400 moles NO₂ are placed in a vessel that 2.0 L. Show by calculation that the reaction is not at equilibrium? What will happen to [O₂] as equilibrium is approached?

6. Consider the following equilibrium:

SO_3(g) + NO_(g) D NO_2(g) + SO_2(g) Keq = 0.500

Exactly 0.100 mole SO₃ and 0.100 mole NO were placed in a 1.00 L flask and allowed to go to equilibrium. Calculate the equilibrium concentration of SO₂.