General Equilibrium 1. What is meant by a reversible reaction? 2. What does the magnitude of the equilibrium constant tell you about the reaction? 3. Why do you need a balanced equation to write the equilibrium constant expression? 4. How does the value of the equilibrium constant relate to rate constants for the reaction? 5. Based on forward and reverse rates, when is equilibrium reached for a reaction? 6. What is meant by a heterogeneous equilibrium? What is the significance of pure solids and liquids in an equilibrium constant expression? 7. Write the equilibrium constant expression, Kc, for the following. a. 2 CO(g) + O2(g) → 2 CO2(g) b. 2 Cl2(g) + 2 H2O(g) → 4 HCl(g) + O2(g) c. H2(g) + F2(g) → 2 HF(g) d. P4(g) + 3 O2(g) → P4O6(s) e. 2 ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g) 8. Calculate K’c for the following given: 2 CO(g) + O2(g) → 2 CO2(g) Kc = 28.9 2 CO2(g) → 2 CO(g) + O2(g) K’c = ? 4 CO(g) + 2 O2(g) → 4 CO2(g) K’c = ? CO2(g) → CO(g) + ½ O2(g) K’c = ? 9. Calculate Kp for the following at 28oC. (R= 0.0821 L atm/mol K) a. 2 CO(g) + O2(g) → 2 CO2(g) Kc = 28.9 b. 2 Cl2(g) + 2 H2O(g) → 4 HCl(g) + O2(g) Kc = 0.0945 c. H2(g) + F2(g) → 2 HF(g) Kc = 11 d. P4(g) + 3 O2(g) → P4O6(s) Kc = 2.33x10-3 e. 2 ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g) Kc = 1.445 10. Determine if each of the following mixtures is at equilibrium. If not, cite the direction in which the reaction is proceeding. a. 2 CO(g) + O2(g) → 2 CO2(g) Kc = 28.9 [CO] = 2.65M , [O2] = 0.986M , [CO2]= 8.99M b. 2 Cl2(g) + 2 H2O(g) → 4 HCl(g) + O2(g) Kc = 0.0945 [Cl2] = 0.578M , [H2O] = 3.35M , [HCl] = 1.25M , [O2] = 0.385M c. H2 (g) + F2 (g) → 2 HF(g) Kc = 11 [H2] = 0.776M , [F2] = 1.09M , [HF] = 2.86M d. P4(g) + 3 O2(g) → P4O6(s) Kc = 2.33x10-3 [P4] = 10.3M , [O2] = 2.86M e. 2 ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g) Kc = 1.445 [O2] = 0.5000M , [SO2] = 2.353M 11. For the following: 2SO2(g) + O2(g) → 2 SO3(g) Kc = 25.5 What concentration of O2 is in equilibrium with 0.450M SO2 and 0.500M SO3? 12. For the following: 2CO2(g) → 2 CO(g) + O2(g) 1.500 mols of CO2 are placed in a 1.000L flask. At equilibrium 1.000 mols CO2 are left in the flask. Calculate Kc for this reaction. 13. For the following: H2(g) + I2(g) → 2 HI(g) 0.850 mols H2 and 0.450 mols I2 are placed in a 1.00L flask. At equilibrium 0.133 mols I2 are left in the flask. Calculate Kc for this reaction. 14. For the following: 4 HCl(g) + O2(g) → 2 Cl2(g) + 2 H2O(g) 1.000 mols of HCl, 1.000 mols O2, 1.000 mols Cl2 and 1.000 mols H2O are placed in a 1.000L flask. At equilibrium 0.600 mols HCl are left in the flask. Calculate Kc for this reaction. 15. Given the following: H2(g) + Cl2(g) → 2 HCl(g) Kc = 21.6 0.250 mols H2 and 0.250 mols Cl2 are placed into a 1.00L flask. Calculate the concentrations of each species at equilibrium. 16. Given the following: 2 HBr(g) → H2(g) + Br2(g) Kc = 0.997 0.485 mols HBr are placed into a 1.00L flask. Calculate the concentrations of each species at equilibrium. 17. Given the following: 2NO2(g) → N2O4(g) Kc = 2.00 1.00 mols NO2 are placed into a 1.00L flask. What is the concentration of N2O4 at equilibrium? 18. Given the following: 2 KClO3(s) → 2KCl(s) + 3 O2(g) Kp = 32.1 KClO3 is heated to a high temperature in a closed container. What is the partial pressure of dioxygen in the flask? 19. State LeChatelier’s Principle. Which stresses on an equilibrium do not result in a change in the value of K? Which do? 20. Based on an energy diagram, explain why a catalyst has no effect on a system at equilibrium. 21. For each of the following equilibrium systems, what would be the effect on increasing the temperature? On decreasing the volume of the container? Comment on both the direction that the equilibrium would shift and the effect on the value of K. a. H2(g) + Cl2(g) → 2 HCl(g) �H= +45.0 kJ b. 2NO2(g) → N2O4(g) �H= -123 kJ c. 2 NOCl(g) → 2 NO(g) + Cl2(g) �H= -55.6 kJ d. PCl5(g) → PCl3(g) + Cl2(g) �H= +411 kJ 22. Comment on both the direction that the equilibrium would shift and the effect on the value of K if some reactant(s) were added to the equilibria systems in problem 21. 23. Comment on both the direction that the equilibrium would shift and the effect on the value of K if some product(s) were removed from the equilibria systems in problem 21. 24. In photosynthesis, the following equilibrium is attained: 6 CO2(g) + 6 H2O(l) → C6H12O6(s) + 6 O2(g) �H= +2801 kJ Comment on both the direction that the equilibrium would shift and the effect on the value of K if a. the amount of CO2 was doubled b. half of the mass of C6H12O6 was removed c. the amount of O2 was doubled d. the amount of H2O was doubled e. the temperature was decreased 25. For each of the following equilibria, Kc was measured at 25oC. Calculate Kc at the new temperature indicated. Kc = 2.00 at 25oC Kc =? at 125oC b. 2 HBr(g) → H2(g) + Br2(g) �Ho= +89.9 kJ/mol Kc = 0.997 at 25oC Kc =? at 15oC c. H2(g) + Cl2(g) → 2 HCl(g) �Ho= -115 kJ/mol Kc = 21.6 at 25oC Kc =? at 85oC d. P4(g) + 3 O2(g) → P4O6(s) �Ho= -45.5kJ/mol Kc = 2.33x10-3 at 25oC Kc =? at 110C a. 2NO2(g) → N2O4(g) �Ho= +32.6kJ/mol 26. Calculate �Go for each of the equations in problem 25 from the equilibrium constant values.