Equilibria

• What happens at equilibrium?

  The rate of the forward and the reverse reaction are equal and the concentrations of the reactants and products are constant.
• Equilibrium can only occur in a...

  Closed system.
• What is Le Chatelier's principle?

  If a system at equilibrium is disturbed, the equilibrium moves in the direction that counteracts that change
• What side of the reaction does pressure move towards?

  The side with fewer moles.
• What side of the reaction does temperature favour?

  The endothermic direction
• Do catalysts have an effect on the position of equilibrium?


  No, but they allow equilibrium to be reached more quickly
• What is the industrial method for preparing hydrogen?

  Using methane and steam reaction
• How does the endothermic nature of the reaction affect equilibrium?

  Equilibrium shifts to RHS with increased temperature
• What is the effect of higher temperature on yield and cost?

  Higher temperature increases yield but is costly
• Why does lower pressure increase yield in this reaction?

  More moles of gas are on RHS
• What is the trade-off of using lower pressure in the reaction?

  Lower pressure means lower costs but low reaction rates
• How does the catalyst affect the yield of the reaction?

  Catalyst has no effect on yield
• What is the benefit of using a lower temperature with a catalyst?

  Lower temperature is less costly
• What is Kc?


  The equilibrium constant.
• Does the products go above or below in the Kc equation?

  Above
• What causes Kc to change?

  A change in temperature
• What do we insert into the Kc equation?

  The concentrations of the reactants and the products.
• Do catalysts have an effect on Kc?


  No
• If one of the reactants has a 2 in front of it, what do we do to the Kc equation?

  We square it
• How do we know that equilibrium has been reached?

  Concentration of the reactants and products is constant
• If the temperature decreases, what happens to Kc?

  Kc decreases
• If Kc increases, what happens to equilibrium?

  Equilibrium shifts right and produces more product
• Kc Formula

  Products concentration / Reactants concentration