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Equilibrium

Equilibrium. Review Lab Reports. Objective/Warm-Up. SWBAT describe equilibrium and determine shifts based on Le Chatelier’s principle. What does the word “equilibrium” mean to you?. Chemical Equilibrium. Chemical equilibrium:

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Equilibrium

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  1. Equilibrium

  2. Review Lab Reports

  3. Objective/Warm-Up • SWBAT describe equilibrium and determine shifts based on Le Chatelier’s principle. • What does the word “equilibrium” mean to you?

  4. Chemical Equilibrium • Chemical equilibrium: • Rate of forward reaction (reactants to products) = rate of reverse reaction (products decomposing to reactants)

  5. Reversible Reactions • The conversion of reactants into products and the conversion of products into reactants occur simultaneously. • Example: 2SO2 + O22SO3

  6. N2 (g) + 3 H2 (g) 2 NH3 (g) Chemical Equilibrium • chemical equilibrium is best represented with a double arrow: • The double arrow is used to indicate that the reaction is an equilibrium reaction. • It indicates that the reaction occurs in both directions simultaneously.

  7. Equilibrium • At equilibrium, the forward and reverse reaction rates are equal. • The concentrations of reactants and products stop changing. • This does NOT mean that the concentrations are equal.

  8. Equilibrium Expressions • Guided Inquiry worksheet

  9. Writing Equilibrium Constants • aA + bB  cC + dD • Keq = [C]c x [D]d [A]a x [B]b • The brackets indicate the concentration in molarity.

  10. Write the Equilibrium Constant • N2O4 2NO2 • H2 + I2  2HI • 3H2 + N2  2NH3 • 2BrCl  Cl2 + Br2

  11. Magnitude of Equilibrium Constants • When Kc (or Kp or Ksp) < 1, more reactants than products are present at equilibrium. N2 (g) + O2 (g) 2 NO (g) Kc = [NO]2 = 1 x 10-30 [N2] [O2] • Equilibrium lies to the left. • Reactants are favored.

  12. Magnitude of Equilibrium Constants • When Kc (or Kp or Ksp) is > 1, more products than reactants are present at equilibrium. CO (g) + Cl2 (g) COCl2 (g) Kc = [COCl2] = 4.57 x 109 [CO] [Cl2] • Equilibrium lies to the right. • Products are favored.

  13. Chemical Equilibrium • CO2 (g) + H2 (g) CO (g) + H2O (l) If a solid or liquid is involved, its concentration is constant and in not included in the equilibrium constant expression. • For this example: Kc = [CO] [CO2][H2]

  14. Calculating Keq 2CO (g) ↔ C (s) + CO2 (g) [CO] = 0.034M [CO2 ] = 0.0045M What is the value of Keq ? Ans: 3.89

  15. N2O4 (g) ↔ 2NO2 (g) [N2O4 ] = 2.0M [NO2 ] = 0.2M What is the value of Keq ? Ans: 0.02

  16. 2ICl (g) ↔ I2 (g) + Cl2 (g) [ICl ] = 2.5 M [I2] = 2.0 M [Cl2] = 1.2 M What is the value of Keq ? Ans: 0.384

  17. Objective/Warm-Up • SWBAT apply LeChatelier’s principle and solve equilibrium problems. • How do you know a reaction is at equilibrium? • Write the equilibrium expression: • 2ICl (g) ↔ I2 (g) + Cl2 (g)

  18. LeChatelier’s Principle • When a stress is applied to a system, the system will try to relieve that stress.

  19. Le Chatelier’s Principle • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/lechv17.swf • http://www.chm.davidson.edu/java/LeChatelier/LeChatelier.html • http://virtual.yosemite.cc.ca.us/smurov/ex14-1.htm

  20. Practice

  21. Q vs. K • http://www.yteach.com/page.php/resources/view_all?id=equilibrium_concentration_Le_Chatelier_dimerisation_oxide_temperature_catalyst_page_0&from=search

  22. Objective/Warm-Up • SWBAT apply LeChatelier’s principle and solve equilibrium problems. • N2O4 (g) 2NO2 (g) • Which way will the above reaction shift if: • More NO2 is added • N2O4 is removed • Pressure is increased

  23. Le Chatelier’s Principle • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/lechv17.swf • http://www.chm.davidson.edu/java/LeChatelier/LeChatelier.html • http://virtual.yosemite.cc.ca.us/smurov/ex14-1.htm

  24. Video

  25. Objective/Warm-Up • SWBAT apply LeChatelier’s principle and solve equilibrium problems. • N2O4 (g) 2NO2 (g) • Which way will the above reaction shift if: • More NO2 is added • N2O4 is removed • Pressure is increased

  26. Objective/Warm-Up • SWBAT apply LeChatelier’s principle and solve equilibrium problems. • Which way will the system shift? • As4O6 (s) + 6 C (s) As4 (g) + 6 CO (g) • Addition of carbon monoxide • Addition of carbon • Removal of carbon • Addition of As4O6 • Removal of As4O6 • Removal of As4

  27. Summary of Le Chatelier’s principle • Amounts of products and reactants: equilibrium shifts to compensate • N2  H2 E.g. N2 + 3H2 2 NH3 + 92 kJ N2 + 3H2 2NH3 + 92 kJ shift right N2 + 3H2 2NH3 + 92 kJ N2 + 3H2 2NH3 + 92 kJ N2 + 3H2 2NH3 + 92 kJ shift left N2 + 3H2 2NH3 + 92 kJ N2 + 3H2 2NH3 + 92 kJ Temperature: equilibrium shifts to compensate:  Heat N2 + 3H2 2NH3 + 92 kJ shift left N2 + 3H2 2NH3 + 92 kJ N2 + 3H2 2NH3 + 92 kJ Pressure (due to decreased volume): increase in pressure favors side with fewer molecules Catalysts: does not influence reaction

  28. Equilibrium of Fish

  29. http://www.yteach.com/page.php/resources/view_all?id=equilibrium_concentration_Le_Chatelier_dimerisation_oxide_temperature_catalyst_page_2&from=searchhttp://www.yteach.com/page.php/resources/view_all?id=equilibrium_concentration_Le_Chatelier_dimerisation_oxide_temperature_catalyst_page_2&from=search

  30. Practice

  31. Group Activity • In groups of 4 people, choose an equilibrium reaction and represent it to the class in some way (poem, skit, song, dance, role play, etc.). • All group members must participate. • Use of props is recommended. • You must include three disturbances and explain their corresponding shifts according to Le Chatelier’s principle.

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