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Equilibrium

Equilibrium . Kinetics and Equilibrium. rate forward = k for [reactants] x and rate reverse = k rev [products] z Since rates are equal at equilibrium, k for [reactants] x = k rev [products] z K eq = [products] z [reactants] x. K’s. Kc - used when dealing with concentrations

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Equilibrium

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  1. Equilibrium

  2. Kinetics and Equilibrium rate forward = kfor[reactants]x and rate reverse = krev [products]z Since rates are equal at equilibrium, kfor [reactants]x = krev [products]z Keq= [products]z [reactants]x

  3. K’s • Kc- used when dealing with concentrations • Kp – used when dealing with partial pressures • Ka- used for acids • Kb – used for bases • Ksp – used for how soluble an ‘insoluble’ salt is

  4. THE SIGNIFICANCE OF K K > 1means that the reaction favors the products at equilibrium Keq = [products]z [reactants]x K < 1 means that the reaction favors the reactants at equilibrium Keq= [products]z [reactants]x K = 1Keq = [products]z [reactants]x

  5. Reaction Quotient-Q • Used if you have concentrations that may or not be equilibrium concentrations. • Can be used predict the direction the reaction will proceed to establish equilibrium. Q > K Q < K Q = K system at equilibrium Q K Shift left (toward reactants) Q K Shift right (toward products) No shift

  6. General steps for solving equilibrium problems A. Write a balanced equation. (* do stoichiometry first in moles if needed). B. Set up equilibrium expression. C. Set up RICE diagram.

  7. “RICE” TABLES --reaction, initial concentration, change in concentration, equilibrium concentration! Never Fails!! R = write a balanced reaction for the predominant reacting species I = fill in the initial concentrations C = what change is taking place E = equilibrium concentrations

  8. Acids and bases • Strong – completely ionizes • Memorize (7 strong acids and the ‘b’ of strong bases • Weak –partially dissociates • If not strong, they are weak.

  9. Buffers Solutions that resist changes in pH when either OH- or H+ ions are added. Example: NH3/NH4+ buffer system HC2H3O2 / C2H3O2- buffer system

  10. Systems that work • weak acid + salt of weak acid • weak base + salt of weak base • weak acid + ½ # of moles of strong base • weak base + ½ # of moles of strong acid • weak acid + weak base

  11. Conjugates • Difference of one H+ (ONLY!!)

  12. Titration Coeff of base x M a x V a = M b X V b x coeff of acid -vol needed for equivalence point

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