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Flashcards for Unit 13

This set of flashcards provides information on equilibrium, including the rates of forward and reverse processes, conditions for equilibrium, types of equilibria, and LeChatelier's Principle. It also covers reversible reactions, chemical equilibrium, catalysts, and pressure and concentration changes in equilibrium systems.

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Flashcards for Unit 13

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  1. Flashcards for Unit 13 Equilibrium

  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. Systems involving gases Whether you are considering phase equilibrium, solution equilibrium, or chemical equilibrium, systems with gases MUST be in a closed container for equilibrium to occur.

  13. Reactions that go to completion So far we have mostly looked at reactions that “go to completion” by Forming a precipitate Forming a gas Forming H2O (neutralization)

  14. Reversible Reactions Don’t go to completion. End up with a mixture of reactants and products in the reaction vessel.

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

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

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

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

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

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

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

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

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

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

  25. 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? Increase pressure by decreasing volume.

  26. By the way: How do we increase or decrease the total pressure? By changing the volume of the container!

  27. 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? Decrease pressure by increasing volume.

  28. 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? Decrease Pressure by increasing volume.

  29. 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?

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

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

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

  33. , the stress. Equilibrium on a graph:Identify the stress & where the system is responding & where the new equilibrium is established. New Equilibrium System responding

  34. Equal Vs. Constant at equilibrium: NOT the same! Forward and reverse rates are equal. Concentration of each species is constant or unchanging, but not necessarily equal to the concentration of anything else.

  35. Shift to the right Forward reaction rate is faster than reverse reaction rate

  36. Shift to the left Forward reaction rate is slower than reverse reaction rate.

  37. Dynamic Equilibrium Macroscopic variables don’t change, but microscopically still a lot going on. Constant flow in two directions, but no net change.

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