1.6 equilibria

• all reversible reactions reach a dynamic equilibrium state where both forward reactions and backward reactions occur at the same rate
• 2 feature of a dynamic equilibrium

  1. forward and backward reactions occur at the same rate
  2. concentration of products and reactants stay constant
• le chataliers principle : when external conditions are changes the equilibrium will shift to oppose that change
• effect of temperature

  • if the temperature increases it will shift in the endothermic direction to absorb the heat
  • if the temperature decreases it will shift in the exothermic direction to release heat
• effect of pressure

  • increasing pressure will shift the position towards the side with fewer moles to reduce pressure]
• effect on concentration

  • adding more products will shift the position backwards to the reactants
• effect on catalyst

  • there will be no change in the position of equilibrium , but will increase the rate of the forward reaction and backwards reaction by the same amount
• • the larger the kc value the greater the amount of products
  • if kc is smaller, the equilibrium favours the ractants
  • kc value only changes with temperature
• the kc value only changes with temperature
• Recycling unreacted reactants back into the reactor can improve the overall yields of all these processes
• Both methanol and ethanol can be used as fuels. If the carbon monoxide used to make methanol in the above reaction was extracted from the atmosphere then it could be classed as carbon neutral. The term carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere” It would only be carbon neutral, however, if the energy required to carry out the reaction was not made by combustion of fossil fuels
• The larger the Kc the greater the amount of products. If Kc is small we say the equilibrium favours the reactants
• whats the effect on kc value if temperature change shifts equilibrium to the right?


  increases
• whats the change in kc value if temperature changes shifts the equilibrium to the left?


  decreases