1 / 25

Equilibrium

Equilibrium. L. Remember this?. Collision theory : reactants only react when they collide at the correct angle and with sufficient energy to do so. Once they collide correctly and with enough energy they form an activation complex (unstable)

kamin
Download Presentation

Equilibrium

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. Equilibrium L

  2. Remember this? • Collision theory: reactants only react when they collide at the correct angle and with sufficient energy to do so. • Once they collide correctly and with enough energy they form an activation complex (unstable) • transition state – physical arrangement of particles during the activation complex • How much energy they require is the activation energy • Types of collisions • Fruitful – forms a product

  3. Reaction rates Fast rxn (More collisions) = less time, faster rate Slow rxn (Less collisions) = more time, slower rate

  4. Slower vs Faster • Change the mechanism • Add steps to the process (inhibitor) • Remove steps (catalyst) • Change the temperature • Change concentration • Pressure (gases) • Less volume to move in, higher concentration • Surface area (solids) • Particle size controls how face a reaction happens

  5. Equilibrium • State of rate balance between two opposing changes • Ex: • Escalader • Treadmill • Haircuts • Nails • Money • 3 types

  6. Reaction equilibrium Rate of Synthesis = Rate of decomposition +

  7. Solution equilibrium Saturated solution Rate of dissolving = rate of precipitation

  8. Phase equilibrium Rate of melting = rate of freezing Rate of vaporization = rate of condensation Rate of sublimation = rate of deposition

  9. Changing equilibrium • Anything that will change the reaction rate will shift the equilibrium • Types of reactants • More reactive = faster reaction • Concentrations • Increased reagents = more chances for collisions • Surface area • Increased exposure to reagents • Temperature • Increased kinetic energy • Addition of a catalyst • Decreases activation energy

  10. Properties of equilibrium Closed system = no change in anything that would affect equilibrium A system at equilibrium will stay that way forever unless some property of the system changes Dynamic – ALWAYS in motion

  11. H2O(l) H2O(g)

  12. So what… • Equilibrium is about RATES, not concentration • At equilibrium the concentration of products does NOT have to equal the concentration of reactants [p] ≠ [r] • Keq = measures how far a reaction gets • Equilibrium constant • Ratio of products to reactants • Can be calculated by setting up a mass action expression • Keq =[p]/[r]

  13. Mass action expression • Keq =[p]/[r] • + = multiply • Coefficients = exponents • Use brackets to signal molar concentration Ex: 2CO2 2CO(g) + O2(g)

  14. Practice N2O4(g) 2NO2(g) CO(g) + 3H2(g) CH4(g) + H2O(g) 2H2S(g)  2H2(g) + S2(g)

  15. Solving for Keq • Simply plug and chug • Find the equilibrium constant for the decomposition of 4M CO2, into 2M CO and 1M O2. 2CO2(g) 2CO(g) + O2(g) Keq = 1

  16. Practice • Calculate Keq given: • N2O4(g) 2NO2(g) • CO(g) + 3H2(g) CH4(g) + H2O(g)

  17. Quick note on Keq Till now we’ve only looked at Homogenous equilibria (all one phase) Since concentration is density (Mol/L) in solids or liquids the density of a PURE substance doesn’t change it remains constant and can be negated In a heterogenous equilibrium (mixed phase) write only substances in the gas phase. I2(s) I2(g) Keq = [I2(g)]

  18. Practice C10H8(s) C10H8(g) CaCO3(s) CaO(s) + CO2(g) C(s) + H(g)O(g) CO(g) + H2(g)

  19. LE CHATELIER’S PRINCIPLE • Life is a see-saw • If stress is applied to a system at equilibrium, the system will shift to relieve that stress • Stress = Change in temperature, concentration, volume or pressure • Keq doesn’t change if concentration, volume or pressure changes

  20. Changing Concentration • SYSTEM WILL ALWAYS SHIFT TO UNDO THE STRESS! • Adding reactants causes a shift towards the products • Removal of products, more products • Removing reactants shifts towards reactants

  21. Changing Temperature • Alters both Keq and equilibrium position • Since Heat can be thought of as either a product or a reactant (endo/exothermic) • Addition of heat will shift an endothermic reaction towards the products • Addition of heat will shift an exothermic reaction towards the reactants • Keq (equilibrium constant) increases in value when the temperature is lowered and decreases when the temperature is raised

  22. Changing Volume/Pressure • Together because you can’t change volume without changing pressure • Only cause a shift if the number of moles of gaseous product is different then the total moles of gaseous reactants • Decreasing Volume/ increasing Pressure shifts gas reactions towards the side with fewer moles • Increasing Volume/ decreasing Pressure shifts gas reactions towards the side with more moles • If number of moles is equal on both sides the system cannot relieve the pressure

  23. Making Le Chatelier work for you More Product More Reactant Add reactant Remove product Change temperature Change pressure Add product Remove reactant Change temperature Change pressure

  24. Practice: Suppose you’re an evil scientist bent on world domination and to power your death ray you need a lot of silver chloride. What are 3 ways you could bend this reaction to your evil will, and then the WORLD! Given: AgCl+ Heat <-->Ag+1 + Cl-1 3 things that would increase [AgCl] Add Ag+1 Add Cl-1 Drop the temperature Fire the LAZER!!!

More Related