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Flashcards for Unit 12

Flashcards for Unit 12. Equilibrium. Rate of forward process = Rate of reverse process. Conditions for Equilibrium. 2-way process Closed System. Dynamic Equilibrium. Macroscopic level – looks constant . Microscopic level – lots of action. Types of Equilibria.

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Flashcards for Unit 12

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  1. Flashcards for Unit 12

  2. Equilibrium Rate of forward process = Rate of reverse process

  3. Conditions for Equilibrium 2-way process Closed System

  4. Dynamic Equilibrium Macroscopic level – looks constant. Microscopic level – lots of action

  5. Types of Equilibria Physical: Phase & Solution Chemical

  6. A solution at equilibrium must be Saturated

  7. Phase Equilibrium H2O(l)  H2O(g)

  8. Solution EquilibriumIonic Cmpd NaCl(s)  Na+(aq) + Cl-(aq)

  9. Solution EquilibriumCovalent Cmpd C6H12O6(s)  C6H12O6(aq)

  10. H2O(g)  H2O(l) Phase Equilibrium

  11. NH4Cl(s)  NH4+(aq) + Cl-(aq) Solution Equilibrium

  12. Chemical Equilibrium – Haber Synthesis N2(g) + 3H2(g)  2NH3(g) + heat

  13. LeChatelier’s Principle A system at equilibrium will respond to remove a stress

  14. What’s a stress for a chemical system? Change in temperature, pressure, or concentration

  15. Catalyst Substance that increases the rate of a chemical reaction without itself being consumed.

  16. Catalyst Does not shift the equilbrium point – the equilibrium concentrations are the same. You just get to equilibrium quicker.

  17. At what temperature can H2O(s) and H2O(l) exist in equilibrium? 0C or 273K

  18. At what temperature can H2O(g) and H2O(l) exist in equilibrium? 100C or 373K

  19. Pressure Changes Only affect systems that have a gas in them

  20. An increase in pressure favors which side? When P , more CO2 dissolves! CO2(g)  CO2(aq)

  21. N2(g) + 3H2(g)  2NH3(g) + heat Equilibrium shifts to right. Concentration of H2 . Concentration of NH3 . Temperature  What happens? Stress

  22. N2(g) + 3H2(g)  2NH3(g) + heat 4 moles 2 moles Shifts to the side with fewer moles of gas, in this case the right. How does this system respond to an increase in pressure?

  23. N2(g) + 3H2(g)  2NH3(g) + heat Shifts to the side with more moles of gas, in this case the left. How does this system respond to a decrease in pressure?

  24. H2(g) + I2(g) + heat  2HI(g) 2 moles 2 moles This system has the same # of moles on each side. It cannot respond to pressure changes. How does this system respond to a decrease in pressure?

  25. NaCl(s)  Na+(aq) + Cl-(aq) This system has no gases. It does NOT respond to pressure changes. How does this system respond to a change in pressure?

  26. N2(g) + 3H2(g)  2NH3(g) + heat Equilibrium shifts to the left. Concentration of N2 & H2 . Temperature . Stress What happens?

  27. N2(g) + 3H2(g)  2NH3(g) + heat Equilibrium shifts to the right. Concentration of N2 & H2 . Temperature . Stress What happens?

  28. N2(g) + 3H2(g)  2NH3(g) + heat Equilibrium shifts to the left. Concentration of N2 . Concentration of NH3 . Temperature . Stress What happens?

  29. Exothermic Reaction Energy is released: It flows from system to environment. Temperature of environment increases.

  30. Endothermic Reaction Energy is absorbed: It flows from environment to system. Temperature of environment drops.

  31. Heat of reaction, H Hproducts - Hreactants

  32. The difference between the potential energy of the products & the potential energy of the reactants? Hproducts – Hreactants or H

  33. H for exothermic rxn H is negative. System has net loss in energy.

  34. H is negative? Exothermic reaction. Products have less potential energy than reactants.

  35. H is positive? Endothermic reaction. Products have more potential energy than reactants.

  36. H for endothermic rxn H is positive. System has net gain in energy.

  37. A + B  C + D + heat Exothermic Reaction. Heat term is on product side.

  38. A + B + heat  C + D Endothermic Reaction. Heat term is on reactant side.

  39. Which phase change is endothermic? Gas to liquid Gas to solid Solid to gas Liquid to solid

  40. Which phase change is exothermic? Solid to gas Liquid to gas Solid to liquid Liquid to solid

  41. A reaction occurs in water & the temperature of the water increases. Endo or Exo? Exothermic

  42. A reaction occurs in water & the temperature of the water decreases. Endo or Exo? Endothermic

  43. A + B  C + D. H = -45 kJ. What is H for C + D  A + B? H = +45 kJ

  44. A + B  C + D. H = -45 kJ. What is H for: 2A + 2B  2C + 2D? H = -90 kJ

  45. Entropy Degree of disorder or chaos in a system.

  46. Entropy The more degrees of freedom a system has, the higher the entropy.

  47. S Entropy

  48. H Enthalpy or Chemical Potential Energy

  49. 0 entropy? A perfect crystal at 0K

  50. S Change in entropy Sproducts – Sreactants

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