Kp

• Kp is the partial pressure constant
• To find Kp all atoms in the equation must be gases
• aA (g) + bB (g) = xX (g) so X goes over A and B because products go over reactants
• P (total) = p(x) + p(A) + p(B)
• unit is atm or Pa
• Smaller Kp value, equilibrium on left
• Bigger Kp value, equilibrium on right
• we don't use a low temp because it gives a slow rate
• Compromise conditions instead of low temp for Haber process:

  • pressure = 200 atm
  • temperature = 350 °C
  • Fe catalyst - increases rate (does not affect position of equilibrium)
  • yield of NH3 = 15%
• partial pressure of an atom = mole fraction x total pressure (given in conditions - mPa)
• mole fraction = moles of atom/total moles