Equilibrium Worksheets

for

Chemistry 12

Mr. Iannone

The following workbook is designed to 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 can’t 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.

Web Site Address: http://www.wjmouat.com/dept/science/chemistry/Iannone/index.html

Notes- double click on the lesson number.

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

Read Hebdon Unit 2

Worksheet #1 Approaching Equilibrium

Read unit II your textbook. Answer all of the questions. Do not start the questions until you have completed the reading. Be prepared to discuss your answers next period.

1. What are the conditions necessary for equilibrium?

Must have a closed system.

Must have a constant temperature.

Ea must be low enough to allow a reaction.

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

In a forward reaction, the reactants collide to produce products and it goes from left to right.

In a reverse reaction, the products collide to produce reactants and it goes form right to left.

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

As the reaction goes to the right, the reaction concentration decreases and therefore, there are less reactant collisions causing the forward rate to decrease.

4. What are the characteristics of equilibrium?

Forward rate is equal to the reverse rate.

The concentration of reactants and products are constant.(not equal)

Macroscopic properties are constant (color, mass, density, pressure, concentrations).

5. Define equilibrium.

Equilibrium occurs when:

Forward rate is equal to the reverse rate.

The concentration of reactants and products are constant.(not equal)

Macroscopic properties are constant. (color, mass, density, pressure, concentrations)

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

The word dynamic means that forward and reverse continue to occur.

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

The reverse reaction rate increases as equilibrium is approached because as the reaction goes from left to right,

the concentrations of the products increases, therefore there are more product collisions causing the reverse reaction rate to increase.

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

8. Reactant concentration. As the reaction goes to the right, the reaction concentration decreases.

9. Products concentration. As the reaction goes from left to right, the concentration of the products increases.

10. Forward reaction rate. The reaction concentration decreases and therefore, there are less reactant collisions causing the forward rate to decreases.

11. Reverse reaction rate. The concentrations of the products increases, therefore there are more product collisions causing the reverse reaction rate to increase.

12. What is equal at equilibrium? The forward and reverse rates are equal.

13. What is constant at equilibrium? The reactant and product concentrations and the macroscopic properties are constant.

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

[reactant] [product] Overall Rate

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 was added to the reaction, what would happen to the PE Diagram, the forward rate, and the reverse rate?

PE Diagram The activation energy would decrease

Forward rate Increase

Reverse rate Increase

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= +58KJ

(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? 15 seconds

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

The container will gradually increase the intensity of brown and then remain constant after 15 seconds.

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 = 1.0 – 0.83 M = 0.034 M / s

5.0 sec

5-10 sec. rate = 0.83 – 0.81 M = 0.004 M / s

5.0 sec

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

The reactant concentration has decreased and the product concentration increased.

The forward rate has decreased and the reverse rate increased and because of this the overall net rate has decreased.

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 = 0.34 – 0.00 M = 0.068 M / s

5.0 sec

5-10 sec. rate = 0.38 – 0.34 M = 0.008 M / s

5.0 sec

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.

It is twice as great because of the stoichiometric relationship. 2moles NO₂

1mole N₂O₄

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

[N₂O₄]= 0.80 M Are they equal? No!

[N0₂] = 0.40 M

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

No it is not. Although the concentrations are constant, the forward and reverse reactions continue forever.

24. What are the necessary conditions to establish equilibrium?

Must have a closed system.

Must have a constant temperature.

Ea must be low enough to allow a reaction.

25. What are the characteristics of an equilibrium?

Forward rate is equal to the reverse rate.

The concentration of reactants and products are constant.(not equal)

Macroscopic properties are constant. (color, mass, density, pressure, concentrations)

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 increases decreases increases right products

2. [H₂] is increased decreases increases increases right products

3. [NH₃] is increased increases increases increases left reactants

4. Temp is increased increases increases decreases left reactants

5. [N₂] is decreased decreases increases decreases left reactants

6. [H₂] is decreased increases decreases decreases left reactants

7. [NH₃] is decreased decreases decreases decreases right products

8. Temp is decreased decreases decreases increases right products

9. A catalyst is added nochange nochange nochange nochange nochange

N₂O_{4 (g)} ⇋ 2NO_2(g) DH = + 92 KJ

Shifts Shifts to Favor the

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

1. [N₂O₄] is increased increases increases right products

2. [NO₂] is increased increases increases left reactants

3. Temp is increased decreases increases right products

4. [N₂O₄] is decreased decreases decreases left reactants

5. [H₂] is decreased nochange nochange nochange nochange

6. [NO₂] is decreased decreases decreases right products

7. Temp is decreased increases decreases left reactants

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 decreases increases increases right products

2. [H₂O] is increased increases increases increases left reactants

3. [O₂] is increased increases increases decreases right products

4. Temp is increased increases decreases increases left reactants

5. [H₂O] is decreased decreases decreases decreases right products

6. [HCl] is decreased increases decreases decreases left reactants

7. [O₂] is decreased decreases decreases increases left reactants

8. Temp is decreased decreases increases decreases right products

9. A catalyst is added nochange nochange nochange nochange nochange

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 nochanges nochanges nochanges

2. CaO is added nochanges nochanges nochanges

3. CO₂ is added increases left reactants

4. Temp is decreased decreases left reactants

5. A catalyst is added nochanges nochanges nochanges

6. [CO₂] is decreased decreases right products

7. Temp is i