3.1.6 Chemical Equilibria

• dynamic equilibrium

  1. rate of forwards and backwards reaction equal
  2. concentration of reactants and products constant
• Temperature increased

  • shift in ENDOthermic direction
  • to reduce temp by absorbing heat
• Temperature decreased

  • shift in EXOthermic direction
  • increase temp by giving out heat
• equilibrium shift to OPPOSE change
• Pressure increase

  • shift to side with fewer gas molecules
• Pressure decrease

  • shift to side with more gas molecules
• lower temps may give

  • higher yield of product

  BUT

  • slow rates of reaction
• high pressure may give

  • higher yield of product
  • faster rate of reaction
  • too high energy costs for pumps too high equipment costs (has to withstand high pressures)
• high pressure may give

  • higher yield of product
  • faster rate of reaction

  BUT

  • too high energy costs for pumps
  • too high equipment costs (has to withstand high pressures)
• Kc

  1. products/reactants
  2. solids not included
  3. raise to power of large balanced numbers
  4. square brackets used
• Kc only depends on temperature
• Kc larger value - higher product yield

  • products predominate
  • equilibrium lies to the right
• Kc smaller value - lower product yield

  • reactants predominate
  • equilibrium lies to the left