Examine the reaction involved in the Haber Process [local]

The Haber process is of great commercial importance; ammonia often is the second or third largest tonnage chemical produced in the US. About Fritz Haber [local].

Temperature Changes: Increasing the temperature will make the reaction occur faster. However, the reaction is exothermic and increasing the temperature will cause the equilibrium to shift left (to produce more reactants) in order to absorb some of the heat that is added.

Concentration Changes: Adding N₂ or H₂ will shift the position of the equilibrium to the right which in turn produces more product. Likewise removal of NH₃ will cause the equilibrium to shift right to make more NH₃.

Pressure Changes: In the equation N_2(g) + 3H_2(g) 2NH_3(g) there are 4 moles of gaseous reactants and 2 moles of products. Increasing the pressure will cause the equilibrium to shift to the side having fewer moles of gas to partially offset the added pressure. Consequently, adding pressure to the system at equilibrium will produce a shift toward making more products. Recall that the pressure of a gas changes with volume. Consequently, it is important to think about equilibrium (of gases) in terms of volume as well.

Adding an inert gas (a gas not involved in the reaction) will not change the equilibrium position. While the total pressure will increase, the partial pressures of the reactants and products in the equation will not change.

Adding a catalyst will lower the activation energy and speed up the rate of reaction. Equilibrium will be reached more quickly, but will have no effect on the equilibrium position.