1 / 18

1850 - 1936

?. 1850 - 1936. Equilibria & Le Chatelier’s Principle. In a reversible reaction a dynamic equilibrium is established when…. Rate of the forward reaction. Rate of the backward reaction. =. 2SO 2 (g) + O 2(g) 2SO 3(g). 3H 2 (g) + N 2(g) 2NH 3(g).

danielle-pena
Download Presentation

1850 - 1936

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. ? 1850 - 1936

  2. Equilibria & Le Chatelier’s Principle • In a reversible reaction a dynamic equilibrium is established when….. Rate of the forward reaction Rate of the backward reaction = 2SO2(g) + O2(g) 2SO3(g) 3H2(g) + N2(g) 2NH3(g)

  3. The equilibrium is established in a closed system – ie. No more reactants added or products removed • Homogeneous system – all species present in the same phase 3H2(g) + N2(g) 2NH3(g) • Heterogeneous system – species present in different phases Hb(s) + O2(g) HbO2(s)

  4. 2SO2(g) + O2(g) 2SO3(g) Forward reaction Backwardreaction Rate Time

  5. Dynamic Equilibrium 2SO2(g) + O2(g) 2SO3(g) 2SO2(g) + O2(g) 2SO3(g) 2SO3(g) 2SO2(g + O2(g)

  6. Le Chatelier’s Principle states… • “A system at equilibria will react to oppose any change imposed upon it.” • Factors affecting equilibria : • Concentration • Pressure • Temperature

  7. How Le Chatelier saved playtime

  8. Changing Concentration Co(H2O)62+(aq)+ 4Cl-(aq) CoCl42-(aq) + 6H2O(l) Add HCl MoreCoCl42- formed Equilibrium shifts to the right Add water More Co(H2O)2+ formed Equilibrium shifts to the left

  9. Changing Concentration 2CrO42-(aq)+ 2H+(aq) Cr2O72-(aq) + H2O(l) Add acid More Cr2O72- formed Equilibriumshifts to the right Add alkali More CrO42- formed Equilibrium shifts to the left

  10. Changing Pressure N2(g) + 3H2(g) 2NH3(g) 2 moles 4 moles Increasing pressure More products formed Fewer moles Smaller volume Equilibrium shifts to the right Favours forward reaction Decreasing pressure Favours backwards reaction More reactants formed More moles Larger volume Equilibrium shifts to the left

  11. Changing Pressure PCl5(g) PCl3(g) + Cl2(g) 2 moles 1 mole Decreasing pressure Equilibrium shifts to the right More products formed More moles Larger volume Favours forward reaction Increasing pressure Favours backwards reaction More reactants formed Fewer moles Smaller volume Equilibrium shifts to the left

  12. Changing Pressure 2HI(g) H2(g) + l2(g) 2 moles 2 moles Decreasing pressure No effect on position of equilibrium 2 moles on each side of equilibrium Increasingpressure

  13. Changing Temperature N2(g) + 3H2(g) 2NH3(g) ΔH – 92kJmol-1 Forward reaction exothermic Increasing temperature Equilibrium shifts to the left Favours endothermic backward reaction More reactants formed Decreasing temperature More products formed Favours exothermic forward reaction Equilibrium shifts to the right

  14. Changing Temperature N2O4(g) 2NO2(g) ΔH + 56kJmol-1 Forward reaction endothermic Increasing temperature More products formed Favours endothermic forward reaction Equilibrium shifts to the right Favours exothermic backward reaction Decreasing temperature Equilibrium shifts to the left More reactants formed

  15. Equilibria & Le Chatelier’s Principle • In a reversible reaction a dynamic equilibrium is established when….. Rate of the forward reaction Rate of the backward reaction = 2SO2(g) + O2(g) 2SO3(g) The concentrations of the reactants & products remain constant when equilibrium is established

  16. Le Chatelier’s Principle states… • “A system at equilibria will react to oppose any change imposed upon it.” • Factors affecting position of equilibria : • Concentration • Pressure – in gaseous equilibria (number of moles of reactants & products) • Temperature (H +ve = endothermic forward reaction) (H -ve = exothermic forward reaction)

  17. These factors affect the position of the equilibria..... What about the effect on the rate at which equilibria is attained ? • Increasing : • Concentration • Pressure • Temperature Increasing each of these factors increases the rate of the reaction Equilibrium is attained faster

  18. Effect of a Catalyst • It increases the rate of the forward and backward reactions equally • A catalyst has no effect on theposition of an equilibrium • However the equilibrium is achieved more quickly.

More Related