equilibria

• N2 + 3H2 <=> 2NH3

  Write an expression for Kc for this equilibrium.

  [NH3]2/[N2][H2]3
• State Le Chateliers principle.

  If a system at equilibrium has is disturbed the equilibrium will shift to counteract the change.
• In the equation:

  CH4+H2O <=> CO+3H2

  Enthalpy change= +210 kJmol -1

  What effect would increasing the pressure have on the position of equilibrium?

  equilibrium will shift to the left.

  This is because the forward reaction is producing more moles of gas than the reverse reaction.
• Suggest and explain why an industrial chemist may use high pressure for the production of hydrogen from:

  CH4+H2O <=> CO 3H2


  The high pressure increases the collision frequency, increasing the rate of reaction.
• What type of system is Kc relevant for?

  Homogeneous systems in equilibrium
• what does Kc being greater or lesser than 1 suggest for the position of equilibrium?

  greater than 1= over to the right

  lesser than 1= over to the left
• What effect does decreasing the temperature in an endothermic reaction have on Kc?

  Kc decreases
• What effect does decreasing the temperature in an exothermic reaction have on Kc?

  Decreasing the temperature in an exothermic reaction increases Kc.