The equilibrium constant K_p is deduced from the equation for a reversible reaction occurring in the gas phase.

K_p is the equilibrium constant calculated from partial pressures for a system at constant temperature.

Students should be able to:
- derive partial pressure from mole fraction and total pressure
- construct an expression for K_p for a homogeneous system in equilibrium
- perform calculations involving K_p
- predict the qualitative effects of changes in temperature and pressure on the position of equilibrium
- predict the qualitative effects of changes in temperature on the value of K_p
- understand that, whilst a catalyst can affect the rate of attainment of an equilibrium, it does not affect the value of the equilibrium constant.