Le Chatelier's principle

• in an equilibrium system:

  rate of the forward reaction is equal to the rate of the reverse reaction

  concentration of products and reactants do not change
• closed system


  isolated from its surroundings, so temperature, pressure and concentrations of products and reactants are unaffected by outside influences
• le chateliers principle

  when a system is in equilibrium and is subjected to external change, the system readjusts itself to minimise the effect of that change
• effect of concentration changes on equilibrium

  if more products are formed, equilibrium shifts to the right

  if more reactants are formed, equilibrium shifts to the left
• effect of temperature changes on equilibrium 


  increase in temperature shifts position of equilibrium to the endothermic direction

  decrease in temperature shifts position of equilibrium to the exothermic direction
• effect of pressure changes on equilibrium


  increasing pressure on the system will shift the position of equilibrium to the side with fewer molecules, reducing the pressure within the system
• effect on a catalyst in the position of equilibrium


  does not change the position of equilibrium, only increases rate at which equilibrium is reached