Equilibrium constant Kp

• When can we deduce Kp?

  Deduced from the equation for a reversible reaction occurring in the gas phase. The system must be at a constant temperature.
• What is Kp?


  Equilibrium constant in terms of partial pressure
• What is partial pressure?


  The pressure exerted by a particular gas in a mixture of gases
• What is the partial pressure symbol?


  Slanted p
• What is partial pressure measured in?


  atm

  OR

  KPa
• For the equation below, write the Kp equation.

  N^2 (g) + 3H^2 (g) ----> 2NH^3 (g)


  Every P = slanted p

  Kp = P^2 (NH^3)

  -------------------

  P(N^2) P^3(H^2)
• What is the equation for partial pressure?


  Partial pressure = mole fraction x total pressure
• Calculate the partial pressure for each reactant and product below when the total pressure is 18atm:

  N^2 (g) + 3H^2 (g) ----> 2NH^3 (g)


  Total number of molecules = 6

  2 NH^3 molecules Mole fraction = 2/6

  3 H^2 molecules Mole fraction = 3/6

  1 N^2 molecule Mole fraction = 1/6

  P(H^2) = 3/6 x 18 = 9

  P(N^2) = 1/6 x 18 = 3

  P(NH^3) = 2/6 x 18 = 6
• How do partial pressure and total pressure relate?


  All the partial pressures added together = total pressure