C19 equilibrium constant Kp

• Kp is the equilibrium constant used for gaseous equilibria
• to calculate Kp, all the reactants and products need to be in a gaseous state
• within a gaseous system, each gas has a partial pressure which adds up to give the total system pressure
• to find the partial pressure of a gas X, use the equation:

  partial pressure = (moles of X/total moles)*total pressure
• partial pressure is normally measured in pascals but can be measured in atmospheres
• Kp is the product of the partial pressures of the products over the product of the partial pressures of the reactants, if there are multiple moles that number becomes a power
• for questions with equilibrium mixtures, to find the number of moles of species at equilibrium use the ICE method:

  • make a table with columns for each species and rows for I C and E
  • I = initial, fill in the initial moles of each species, given in the question
  • C = change, fill in how much the moles of any species with known changes changed by
  • divide the change by the molar ratio of the known changing species and multiply it by the molar ratio of an unknown changing species to get each unknown change
  • E = equilibrium, fill in the moles at equilibrium by adding together initial and change