Chatelier's Principle

• A system wants to be balanced, so when stress is applied, the system will shift or move to either

  • restore balance
  • minimize change
• when a system at eq is disturbed, it will find a new eq
• A stress is applied to the whole system; the whole system shifts and a new eq is established
• Ways to disturb the eq system:

  1. Concentration
  2. Temperature
  3. Pressure and volume changes (gases only)
  4. Catalyst (reaches eq faster)
  5. Inert gas (has no effect, unreactive)
• increasing []: the system shifts away from it, consumes it
• decreasing []: the system will shift towards it, replacing it
• chaning temperature will change the Kc value
• Temperature change:

  • endo or exo?


  might have to use formation table or Hess' law
• **treat temperature + the energy term like a reactant or a product

  • Add -> shift away
  • remove -> shift towards
• Pressure and volume changes (gas only)

  • increase volume : decrease pressure : decrease concentration
  • decrease volume : increase pressure : decrease concentration
• will shift to the side with either less or more moles (depending on what was changed). No shift if amount of moles are equal on each side
• on a graph, a pressure/volume change can be recognizes by all system entities either going up or going down at the same time