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Topic: EQUILIBRIUM Do Now:

Topic: EQUILIBRIUM Do Now:. VIDEO CLIP. Equilibrium = Balance Not necessarily equal. 1 man and 1 man equal but not balanced. BALANCED!. Chemical equilibrium. Rate of forward reaction is EQUAL to the Rate of the reverse reaction

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Topic: EQUILIBRIUM Do Now:

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  1. Topic: EQUILIBRIUMDo Now:

  2. VIDEO CLIP

  3. Equilibrium = BalanceNot necessarily equal 1 man and 1 man equal but not balanced

  4. BALANCED!

  5. Chemical equilibrium Rate of forward reaction is EQUAL to the Rate of the reverse reaction Concentrations are not necessarily equal but they are constant, unchanging

  6. N2(g) + 3H2(g)  2NH3(g) H2 NH3 N2 Time EQUILIBRIUM POINT Concentration

  7. Dynamic Equilibrium • macroscopic level • looks like nothing is happening • microscopic level • lots going on

  8. Phase Equilibrium phase changes are reversible processes • H2O(l)  H2O(g) • H2O(l)  H2O(s) same substance on both sides, only its phase is different NOTE: anytime a gas is involved, the container must be sealed for equilibrium to be reached- if not the gas will escape! Liquid – Vapor Equilibrium

  9. Solution Equilibrium • saturated solution with some solid on the bottom of the container. • As one molecule dissolves, one molecule precipitates (forms solid). • Ex: Too much sugar in the coffee. - EX: CO2in water CO2(g)  CO2(aq) favored by high pressure & low temperature

  10. Reversible Reactions • Most chemical reactions are reversible. • Reactants react to form Products, then the Products react to form Reactants. • N2(g) + 3H2 (g) 2NH3(g) • N2 reacts with H2to form NH3 • at the same time, NH3 is consumed and formsN2 and H2

  11. Reversible Rxnvs Reaction that goes to completion NaOH + HCl--> NaCl + H2O

  12. equilibrium can be changed or affected • changes in concentration, pressure, temperature affect forward & reverse reactions differently • compositionof equilibrium mixture will shift to accommodate these changes

  13. Le Chatelier’s Principle • When a system at equilibrium is subjected to a stress, the equilibrium will shift in the direction which tends to relieve the stress. • stress = change in concentration, volume, pressure, or temperature

  14. Increase Concentration • INCREASINGthe concentration causes the equilibrium to shift AWAY from the substance that was added.

  15. N2 + 3H2 2NH3 • Increase N2 At equilibrium In order to get back to equilibrium, what has to happen? Need more products! Rxn shift to the RIGHT What happens to the amount of H2?

  16. N2 + 3H2 2NH3 • Increase NH3 Need more N2 and H2 so reaction shifts to the left

  17. DECREASING the concentration causes the equilibrium to shift TOWARD the substance that was removed.

  18. N2 + 3H2 2NH3 • Decrease NH3 Need more NH3 so reaction shifts to the right

  19. Changes in Temp shift in the direction opposite of the “heat” term • exothermic reaction: A + B  C + D + heat • If ↑ temperature, system shifts to consume heat so shifts to left  • so endothermic rxnfavored • endothermic reaction: A + B + heat  C + D • If ↑ temperature, system shifts to consume heat so shifts to right • so exothermic rxnfavored

  20. !! PRESSURE !! • Increase PRESSURE, shift toward the side of the equation that has LESS MOLES of GAS. • Decrease Pressure, shift toward the side of the equation that has MORE MOLES of GAS. N2(g) + 3H2(g)  2NH3(g)

  21. VOLUME • Increasing Volume decreases pressure. • Equilibrium will shift toward greater number of moles of gas. • Decreasing Volume increases pressure. • Equilibrium will shift toward smaller number of moles of gas.

  22. Reactions that go to completion – equilibrium can not exist Formation of a gas which escapes H2CO3 (aq)  CO2(g) + H2O (l) Formation of water HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Formation of a precipitate (insoluble compound) NaCl (aq) + AgNO3(aq)  AgCl (s) + NaNO3 (aq)

  23. Stress Equil. Shift [A] [B] [C] [D] [A] ______ [D] ______ [C] ______ [B] ______ A + B  C + D DEC  INC  INC  right INC  INC  DEC  left right DEC  DEC  INC  INC  DEC  DEC  left

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