Summary: Chem105

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• 2 EQUILIBRIUM

• 2.1 equilibrium (Le Chateliers Principle)

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• What is chemical equilibrium

   - The state when concentrations of both reactants and products remain constant with time
  - rate of product formed = rate of reactant formed

• What are the characteristics of chemical equilibria?

  1. Is a mixture of reactants and products
  2. The composition of the mixture no longer changes 
     concentration of reactants =/ concentration of products
  3.  It is dynamic equilibrium (has both forward and reverse reaction)
  4. The dynamic equilibrium can be controlled.

• How to find the direction of a reaction? 

  You must compare Q to K
  

  • If Q<K : it will proceed to the right to reach equilibrium
  • If Q>K : it will proceed to the left to reach equilibrium
  • If Q = K : there will be no shift in the system (equalibrium)

• Which phases do not have concentrations or pressures?

  1. Pure solids
  2. Pure liquids 
  
  ** must substitute it for a 1 instead**   

• What does the magnitude of the Equilibrium Constant represent?

  It indicates the extent to which the forward and reverse reaction takes place

• What does Intermediate K represent? (equilibrium constant)

  10^-3 < K < 10^2
  

  • At equilibrium [ significant amounts of both products and reactants ]

  ** some weak acids have intermediate Ka values**
   

• What does Small K represent? (equilibrium constant)

  K < 10^-4
  

  • At equilibrium [ small products and large reactants]
  • reaction does not proceed much at all (reactants side) 
  • An example of Ksp (solubility equilibria)

• What are the relationships of equilibrium constants?

  1. Reverse reaction is the reciprocal of forward reaction 
     
  2. Multiplying a reaction by factor n, you must raise K to that nth power

• What happens to Q when you start with CD but with no AB? (Direction of Equilibrium?)

  (CD)/(AB) = (AB)/(0) = infinity 
  
  Therefore it will shift to the left

• What is the Le Chateliers Principle?

  • If a change occurred in the reaction (concentration, temp, catalyst, volume, pressure) at equilibrium then it will shift in the direction that will reduce the change 
  • It will try to balance out