Equilibrium

• What is dynamic equilibrium

  Rate of forwards reaction = role of backwards reaction and the concentrations of the reactants and products do not change
• what is homogeneous law

  all of the equilibrium species have the same state or phase
• what is equilibrium law 


  kc equation
• Equilibrium ratio practice - draw out the table

  image shown below

  
• What is kp

  The equilibrium constant in terms of partial pressure
• what is mole fraction of a gas

  = number of moles in A / total number of moles in gas mixture
• what is partial pressure

  mole fraction x total pressure
• What should the sum of partial pressures equal

  The total pressure
• what are the units for kp

  kpa
• what happens to K if there is a change in concentration ie N2O4 –> 2NO2


  worked example : kc = [NO2]2 / [N2O4] 0.4 2 / 0.1 = 16dm3 , but if you double conc then no longer in equilibrium 0.4 2 / 0.02 = 8 dm3

  word example : if you increase the [N2O4] no longer in equilibrium . the concentration of N02 must increase and the concentration of N204 decreases to restore the kc ratio therefore equilibrium shifts right
• what happens to k if there is a change in pressure e.g N2O4 –> 2NO2

  Worked example : kp = p(NO2)2 / P(N2O4) = 9.6 2 /0.24 = 384 atm

  so if you double the pressure , 19.2 2 / 0.48 = 768 atm

  written example - therefore if you double the pressure the reaction is no longer in equilibrium so the decreased pressure of N02 and increase the pressure of N204 to restore kp
• what happens to k if there is a change in temperature e.g

  H20 + CO ==> H2 + CO2 delta H = - 412 kjmol-1

  the forward reaction is exothermic

  worked example kc = [H2] [CO2] / [CO] [H20]

  worded example : reverse reaction is exothermic so if you increase the temperature is no longer in equilibrium . The concentration of products will decrease and the concentration of reactants increase to achieve the ratio for the new kc ( kc Is smaller so equilibrium shifts left )