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15.4

15.4. What does it mean if Keq is large? Small? Apply stoichiometry to determine Keq’s HW: 15.5 form. Quick review. What is equilibrium? What is Keq , conceptually? What is the Keq expression for: 2SO 3 (g)  2SO 2 (g) + O 2 (g). Packet O’ Practice. 8,10,11,12,13,14, 41. Do Now.

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15.4

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  1. 15.4 • What does it mean if Keq is large? Small? • Apply stoichiometry to determine Keq’s • HW: 15.5 form

  2. Quick review • What is equilibrium? • What is Keq, conceptually? • What is the Keq expression for: • 2SO3(g)  2SO2(g) + O2(g)

  3. Packet O’ Practice • 8,10,11,12,13,14, 41

  4. Chem. 116 Prof. T.L. Heise

  5. Chem. 116 Prof. T.L. Heise

  6. Chem. 116 Prof. T.L. Heise

  7. Do Now • What were the big ideas for 15.5? Be prepared to share. Don’t be afraid to consult your notes/summary.

  8. Objectives • Use Keq to predict direction of reaction based on initial reactions • Determine equilibrium concentrations based on initial conditions

  9. 2SO3(g)  2SO2(g) + O2(g) • Keq=4.08 x 10-3 • Initial concentrations are: [SO3] = 2 x 10-3 M, [SO2] = 5 x 10-3 M, and [O2] = 3 x 10-2 M? • Which way will the reaction proceed in order to reach equilibrium?

  10. 2SO3(g)  2SO2(g) + O2(g) • Keq=4.08 x 10-3 • Initial concentrations are: [SO3] = 2 x 10-3 M, [SO2] = 5 x 10-3 M, and [O2] = 3 x 10-2 M? • What will the equilibrium concentrations be?

  11. Your turn: • Packet O’ Practice: • 38 (and actually determine EQ concentrations for each compound), 39, 40, 41

  12. Todays goals • Practice ICE box type problems • Discuss Le Chatelier’s principle • Test is Wednesday • Please complete 15.6 form • Lab on Monday (hopefully…) • Kinetics lab due tomorrow

  13. Packet o’ practice • 38 (and actually determine EQ concentrations for each compound), 39, 40, 41

  14. Chem. 116 Prof. T.L. Heise

  15. Chem. 116 Prof. T.L. Heise

  16. Chem. 116 Prof. T.L. Heise

  17. Chem. 116 Prof. T.L. Heise

  18. Le Chatelier’s principle • Changing the following will disturb an equilibrium: • Changing [reactant/product] • Add-> away • Remove -> replace • Changing pressure • Favors side with less moles of gas • Changing temperature • Treat it like a chemical…

  19. Remember • A catalyst increases the forward AND reverse reactions rates… • No change overall…

  20. 58 Sample Exercise: For the reaction PCl5(g) + energy  PCl3(g) + Cl2(g) in what direction will the equilibrium shift when (a) Cl2(g) is added (b) the temperature is increased (c ) the volume is decreased (d) PCl5(g) is added Chem. 116 Prof. T.L. Heise Chem 116: Prof. T.L. Heise Chem 15.6

  21. How would Keq change with increasing the temperature? • 2POCl3(g) + energy  2PCl3(g) + O2(g) use this result to determine how the equilibrium constant for the reaction should change with temperature. Keq = [PCl3]2[O2] [POCl3]2

  22. Chem. 116 Prof. T.L. Heise

  23. Chem. 116 Prof. T.L. Heise

  24. Do Now • Turn in Kinetics Lab • The decay of a radioactive isotope is first order and has a half-life of 10days. How long will it take for 65% of it to decay?

  25. Whats the rate law?

  26. Quick rundown by chapter: • CH14 stuff: • Overview • Rxn order from data • Stoichand rxn rates • Rxnmech and rate law (intermediates, catalysts, etc) • Mechanism general info • [X]left after time • ½ life problems… • Catalyst and what they do… • Factors affecting rxn rate • Graphing and rate order

  27. Ch 15 • Big idea stuff • Keq expression and determining value • Heterogenouseq… • Determining direction of reaction (Q vsKeq) • ICE question, new conc from Keq • Determining [x] given Keq and data • High vs low Keq, whats it tell you • Le chat, determine changes and ID stress from changes • Catalysts and their effects…

  28. Review by looking at the lab • Determining Keq given one of the concentrations…

  29. Review by looking at the lab • What happened when we added NH4Cl? • Why? (Le Chaet’ and Keq)

  30. Review by looking at the lab • Determining eqconcetrations of NH3, NH4+, OH- (use the accepted keq) • Initial? Change? Eq?

  31. 3. The half-life of a radioisotope is found to be 4.55 minutes. If the decay follows first order kinetics, what percentage of isotope will remain after 2.00 hours?

  32. Chem. 116 Prof. T.L. Heise

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