1 / 19

Le Chatelier’s Principle

Le Chatelier’s Principle. Chem 12 - Unit 3. Le Chatelier’s Principle. The French chemist Henri Le Chatelier (1850-1936) studied how the equilibrium position shifts as a result of changing conditions. LeChatelier’s Principle.

ferris-ross
Download Presentation

Le Chatelier’s Principle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Le Chatelier’s Principle Chem 12 - Unit 3

  2. Le Chatelier’s Principle • The French chemist Henri Le Chatelier (1850-1936) studied how the equilibrium position shifts as a result of changing conditions

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

  4. Le Chatelier 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 shifts in such a way as to use up what you’ve added.

  5. What items did he consider to be stress on the equilibrium? • Concentration • Temperature • Pressure

  6. Examples: • Let’s look at some examples, there will be a summary table at the end!

  7. Le Chatelier 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

  8. Le Chatelier Example #2 A closed container of N2O4 and NO2 at equilibrium.NO2 is addedto the container. N2O4 (g) + Energy  2 NO2(g) The equilibrium of the system shifts to the _______ to use up the added NO2. left

  9. Le Chatelier Example #3 A closed container of water and its vapor at equilibrium.Vapor is removedfrom the system. water + Energy  vapor The equilibrium of the system shifts to the _______ to replace the vapor. right

  10. Le Chatelier Example #4 A closed container of N2O4 and NO2 at equilibrium. Thepressureisincreased. 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

  11. Pressure Changes to system: • If the volume decreases, the concentration increases, and there will be a shift to the side with the less amount of moles. • If the volume increases, the concentration decreases, and there will be a shift to the side with the more amount of moles.

  12. Another Example: • If I increase the pressure, where is the shift? (right) • If I decrease the pressure, where is the shift? (left) 2SO2 + O2<--> 2SO3 (3moles) (2moles)

  13. Effect of Concentration: • If you add more reactant, it shifts to the right increasing the formation of product, using up the reactants. • If you add product, it shifts to the left • If you remove product, it shifts to the right, increasing the formation of product. • If you remove reactant, it shifts to the left

  14. Effect of temperature: • Remember: Energy is treated as a reactant if endothermic equation and as a product if exothermic equation. • If heating a system, it shifts so extra heat is used up. • If cooling a system, then it shifts so more heat is produced.

  15. Example Endothermic Reaction: • Heating this reaction causes the system to shift to the right = more products, because you treat energy like a reactant (this reaction needs energy to go forward) 2NaCl +H2SO4 + energy < -- > 2HCl + Na2SO4 • Cooling this reaction causes the system to shift to the left = less reactants, so need to make up more

  16. Example Exothermic Reaction: • Heating this reaction causes the system to shift to the left, to use up the extra heat. 2SO2 + O2<--> 2SO3 + energy • Cooling this reaction causes the system to shift to the right, to make up for the lost heat.

  17. Common Ion Effect: • Involves adding of an ion to a solution in which the ion is already present in the solution • Increases concentration of that ion • Eq shifts away from that ion Example: Cu2+(aq) + 4Cl-1 <-> CuCl42+ (aq) Adding NaCl would increase the Cl-1 concentration and shift Eq right!

  18. Try it : • Handouts • Page 529 #33-37

More Related