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Chemical Equilibrium Chapter 18 Modern Chemistry
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  1. ChemicalEquilibriumChapter 18 Modern Chemistry Sections 1 & 2 The Nature of Chemical Equilibrium Shifting Equilibrium Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  2. Section 18.2 Shifting Equilibrium Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  3. Seesaws and Equilibrium Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  4. LeChatelier’s PrincipleA play in one act. Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  5. TEACHER:“Let’s put stress on the equilibrium!” STUDENTS:“How?”(puzzled) TEACHER:“Change the T, P, or concentration.” LECHATELIER:“A new equilibrium will be attained.” STUDENTS:“How?”(amazed) TEACHER:“One of the reactions will go faster, for a while, to relieve the stress.” STUDENTS:“I understand.”(with confidence) Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  6. The End. Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  7. LeChatelier’s Principle Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  8. LeChatelier’s Principle • If a system at equilibrium is subjected to a stress, the equilibrium is shifted in the direction that tends to relieve the stress…and a new equilibrium is achieved. Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  9. How is a system “stressed”? • Changing the concentration • Adding a reactant or product • Removing a reactant or product • Changing the temperature. • Changing the pressure Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  10. Changes in Pressure • Affects only eq. with gases • Increasing the pressure favors the side with the fewest particles • Leading to a decrease in pressure • Decreasing the pressure favors the side with the most particles • Leading to an increase in pressure • If particle are equal, pressure has no effect. • Increasing pressure by adding a gas that is not a reactant or a product cannot affect the eq. Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  11. Balanced Equation • 2NO2 (g)  N2O4 (g) + Energy • O2 (g) + 2SO2 (g) + Energy  2SO3 (g) • N2 (g)+ 3 H2 (g) 2NH3 (g)+ Energy • 2HI(g)+ Energy  H2 (g)+I2 (g) • O2 (g) + N2 (g) 2NO2 (g) • Keq = 4.5 x 10-31 at 25 ° C • Keq = 6.7 x 10-10 at 627 °C Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  12. Complex Ions • Central Metal • Surrounded by ligands • Examples of ligands • H2O • NH3 • CN1- • Cl1- Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  13. Changes in Concentration • Increase the concentration of reactants • the forward reaction is favored • Increase the concentration of products • the reverse reaction is favored Up, Up and Away Take Away Towards Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  14. Complex Cu Ion System UP, UP AWAY [Cu(H2O)4 ] 2+ + 4Cl1-  [CuCl4]2- + 4H2O Green Blue • Increase Cl1- • Shift is forward • Products increase, reactants decrease • The Keq is the same – before and after Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  15. Complex Cu Ion System UP, UP AWAY [Cu(H2O)4 ] 2+ + 4Cl1-  [CuCl4]2- + 4H2O Green Blue • Increase H2O • Shift is reverse • Reactants increase, products decrease • The Keq is the same – before & after Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  16. Complex Co Ion System TAKE AWAY [CoCl4]2- + 6H2O  [Co(H2O)6]2+ + 4Cl- TOWARDS Pink Blue • Decrease H2O • Shift is reverse • Reactants increase, products decrease • The Keq is the same – before & after Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  17. Balanced Equation • 2NO2 (g)  N2O4 (g) + Energy • O2 (g) + 2SO2 (g) + Energy  2SO3 (g) • N2 (g)+ 3 H2 (g) 2NH3 (g)+ Energy • 2HI(g)+ Energy  H2 (g)+I2 (g) • O2 (g) + N2 (g) 2NO2 (g) • Keq = 4.5 x 10-31 at 25 ° C • Keq = 6.7 x 10-10 at 627 °C Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  18. Changes in Temperature 2NO2 (g)  N2O4 (g) + Energy • In a reversible reaction one direction is exothermic and the other direction is endothermic. • In the reaction above which direction is • exothermic? • forward • endothermic? • reverse Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  19. Changes in Temperature 2NO2 (g)  N2O4 (g) + Energy • Increasing the energy favors the endothermic reaction • Decreasing the energy favors the exothermic reaction • Keq is dependant on temperature • A change in temp, changes the Keq. Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  20. Equilibrium Constants Table Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  21. NO2 N2O4 System Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  22. NO2 N2O4 System AWAY 2NO2 (g)  N2O4 (g) + Energy UP, UP Brown Colorless • Increase Energy (temperature) • Shift is reverse • Products decrease, reactants increase • The Keq is decreasing Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  23. NO2 N2O4 System TOWARDS TAKE AWAY 2NO2 (g)  N2O4 (g) + Energy Brown Colorless • Decrease Energy (temperature) • Shift is forward • Products increase, reactants decrease • The Keq is increasing Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  24. Changes in Temperature Pb(s) + PbO(s) + 2H2SO4(aq)2PbSO4(s) + 2H2O(l) + E engine running storing energy that is taken in engine not running using energy that is given off Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  25. Balanced Equation • 2NO2 (g)  N2O4 (g) + Energy • O2 (g) + 2SO2 (g) + Energy  2SO3 (g) • N2 (g)+ 3 H2 (g) 2NH3 (g)+ Energy • 2HI(g)+ Energy  H2 (g)+I2 (g) • O2 (g) + N2 (g) 2NO2 (g) • Keq = 4.5 x 10-31 at 25 ° C • Keq = 6.7 x 10-10 at 627 °C Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  26. Effect of T, P & Conc Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  27. Chickens Lose Equilibrium CO2(g) CO2(aq) H2CO3(aq) H+ + HCO3- (aq)  H+ + CO3-2(aq) + Ca2+ CaCO3(s) EGGSHELL CHICKEN BREATH Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  28. Reactions that go to completion • If a product leaves the system the reaction will not reverse. It will go to completion. • Formation of a gas. • H2CO3 (aq) H2O(l) + CO2(g) • Formation of a precipitate. • Na+(aq)+Cl−(aq)+Ag+(aq)+NO3−(aq) Na+(aq)+NO3−(aq)+AgCl (s) Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  29. Common Ion Effect Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  30. Common Ion Effect UP, UP AWAY • The addition of HCl caused the NaCl to increase and precipitate out of solution. • Common-ion Effect - the addition of an ion common to two solutes brings about precipitation or reduced ionization. HCl (g) H+(aq) + Cl−(aq) NaCl (s) Na+(aq) + Cl−(aq) Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  31. Common Ion Effect NaC2H3O2  Na+ + C2H3O2- • Adding acetate ion from the dissociation of sodium acetate causes a reverse shift. • Ionization is reduced. [H3O+] is reduced. AWAY UP, UP HC2H3O2(aq)+ H2O(l)H3O+(aq)+ C2H3O2−(aq) Chapter 18 Section 2 Shifting Equilibrium p. 598-604

  32. Ch 18 Sec 2 Homework LeChatelier’s Principle Worksheet Chapter 18 Section 2 Shifting Equilibrium p. 598-604