1.06 equilibrium

• What is dynamic equilibrium?

  When the forward and backward rate of reaction in a closed system is the same and remains constant.
• What is activation energy?

  the minimum amount of energy needed for a reaction to occur with sucessfull collisions
• What does Le Chatelier's Principle state?

  If an external condition is changed the equilibrium will shift to oppose the change
• What are the two features of dynamic equilibrium?

  Forward and backward reactions are occurring at

  equal rates.

  
  

  The concentrations of reactants and products stay constant
• If equilibrium position favours left what will there be more of?

  Reactants.
• If equilibrium position favours right what will there be more of?

  Products
• What is Le Chatelier's principle?

  The idea that if you change the conditions of a reversible reaction at equilibrium, the position of equilibrium will shift to counteract that change.
• If temperature increases what happens to the position of equilibrium?

  If temperature is increased the equilibrium will shift to oppose this and move in the endothermic direction to try to reduce the temperature by absorbing heat.
• If temperature decreases what happens to the position of equilibrium?

  If temperature is decreased the equilibrium will shift to oppose this and move in the exothermic direction to try to increase the temperature by giving out heat.
• If pressure increases what happens to the position of equilibrium?

  Increasing pressure will cause the equilibrium to shift towards the side with fewer moles of gas to oppose the change and thereby reduce the pressure.
• If pressure decreases what happens to the position of equilibrium?

  Decreasing pressure will cause the equilibrium to shift towards the side with more moles of gas to oppose the change and thereby increase the pressure.
• What are the problems with increasing pressure too high?

  Increasing pressure may give a higher yield of product and will produce a faster rate. Industrially high pressures are expensive to produce ( high electrical energy costs for pumping the gases to make a high pressure) and the equipment is expensive (to contain the high pressures)
• What's the problem with too high temperatures?

  Expensive and dangeous
• What's the problem with too low temperatures?

  Slow rate of reaction
• What is the effect of increase the concentration of the reactants?

  Increasing the concentration of reactants causes the equilibrium to shift to oppose this and move in the forward direction to remove and decrease the concentration of reactants. The position of equilibrium will shift towards the right, giving a higher yield of products.
• If concentration of A increases what happens to the position of equilibrium?

  Equilibrium shifts away from A.
• If concentration of A decreases what happens to the position of equilibrium?

  Shifts towards A.
• What is the effect of a catalyst on the position of equilibrium?

  A catalyst has no effect on the position of equilibrium, but it will speed up the rate at which the equilibrium is achieved.

  
  

  It does not effect the position of equilibrium because it speeds up the rates of the forward and backward reactions by the same amount.
• What are the ideal conditions for this reaction to increase yield of ammonia?

  
  

  N2 + 3H2 ⇌ 2NH3

  
  

  Enthalpy change = negative/exo

  
  

  T= 450, P= 200 - 1000 atm, iron catalyst

  The temperature should be decreased as this will cause the equilibrium to shift to oppose this and move in the exothermic/forwards direction to try to increase temperature. This means the position of equilibrium will shift towards the right, giving a higher yield of ammonia. However, decreasing the temperature will decrease the rate of reaction so a compromised temperature is used.

  
  

  The pressure should be increased as this will shift the equilibrium to oppose this and move towards the side with fewer moles of gas to try to reduce the pressure . The position of equilibrium will shift towards the right because there are 4 moles of gas on the left but only 2 moles of gas on the right, giving a higher yield of ammonia. However too high of a pressure will cause high energy costs for pumps to produce the pressure and high equipment costs for equipment that can withstand the pressure.
• What is one way to increase yield no matter what?

  Recycling unwanted reactants back through.
• What is the formula for Kc?

  [products]^moles /[reactants]^moles
• Does a change in concentration affect Kc?

  No.
• Does the use of a catalyst affect Kc?

  No.
• Does a change in temperature affect Kc?

  Yes.
• Does a change in pressure affect Kc?

  No.
• What is the effect of changing temperature on Kc?

  Depending on the temperature, if equilibrium shifts to produce less products then Kc will get smaller.