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Equilibrium and Le Chatelier’s Principle

Equilibrium and Le Chatelier’s Principle. What is Equilibrium?. Equilibrium Crash Course. Chemical Equilibrium. Reversible Reactions :. A chemical reaction in which the products can react to re-form the reactants. Chemical Equilibrium :. When the rate of the forward reaction

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Equilibrium and Le Chatelier’s Principle

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  1. Equilibrium and Le Chatelier’s Principle

  2. What is Equilibrium? • Equilibrium Crash Course

  3. Chemical Equilibrium Reversible Reactions: A chemical reaction in which the products can react to re-form the reactants Chemical Equilibrium: When the rate of the forward reaction equals the rate of the reverse reaction and the concentration of products and reactants remains unchanged 2HgO(s)  2Hg(l) + O2(g) Arrows going both directions ( ) indicates equilibrium in a chemical equation

  4. Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low and the system is closed. Reactants⇌Products

  5. Approaching Equilibrium Many chemical reactions are reversibleif the activation energy is low. Reactants⇌Products Forward Reaction is left to right Reverse Reaction is right to left

  6. Approaching Equilibrium Reactant concentrationsstart high and decreaseas the reaction proceeds. The forward rate, which depends on collisions of the reactants, also decreases. Product concentrationsstart at zero andincreaseas the reaction proceeds. The reverse rate, which depends on collisions of the products, also increases. Eventually the forward rateis equal to the reverse rateand the concentrationsare constant.This is equilibrium.

  7. Graphing the Approach to Equilibrium Forward rate  Concentration Reverse rate Overall rate Time

  8. LeChatelier’s Principle Henry Le Chatelier • When a system at • equilibrium is placed under stress, the system will undergo a change in such a way as to relieve that stress.

  9. LeChatelier Translated: • When you take something away from a system at equilibrium, the system shifts in such a way as to replace what you’ve taken away. When you add something to a system at equilibrium, the system shiftsin such a way as touse up what you’ve added.

  10. Video Clip • http://www.youtube.com/watch?v=7zuUV455zFs

  11. LeChatelier Example #1 A closed container of ice and water at equilibrium. The temperature is raised. Ice + Energy  Water The equilibrium of the system shifts to the _______ to use up the added energy. right

  12. LeChatelier Example #2 A closed container of N2O4 and NO2 at equilibrium. NO2 is added to the container. N2O4 (g) + Energy  2 NO2(g) The equilibrium of the system shifts to the _______ to use up the added NO2. left

  13. LeChatelier Example #3 A closed container of water and its vapor at equilibrium. Vapor is removed from the system. water + Energy  vapor The equilibrium of the system shifts to the _______ to replace the vapor. right

  14. LeChatelier Example #4 A closed container of N2O4 and NO2 at equilibrium. The pressure is increased. N2O4 (g) + Energy  2 NO2 (g) The equilibrium of the system shifts to the _______ to lower the pressure, because there are fewer moles of gas on that side of the equation. left

  15. Now you try….. • Predict what will happen in each of the following situations:

  16. The Forward and Reverse Rates and Shifting Explainin terms of the immediate changes to the forward andreverserates after each stress why each shift occurs 2CO(g) + O2(g) ⇄ 2CO2(g) + energy Shift Forward Reverse Some CO is added- more reactant collisions. Right Increases No change

  17. The Forward and Reverse Rates and Shifting Explain in terms of the immediatechanges to the forwardandreverserates after each stress why each shift occurs 2CO(g) + O2(g) ⇄ 2CO2(g) + energy . CO is removed Shift Forward Reverse left decreases same

  18. The Forward and Reverse Rates and Shifting Explain in terms of theimmediatechanges to the forwardandreverserates after each stress why each shift occurs 2CO(g) + O2(g) ⇄ 2CO2(g) + energy Temperature is increased- Shift Forward Reverse We know it shifts left both forward and reverse rates increase. left increases increases by more

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