Why are the optimum conditions for the Haber process a temperature of 450°C and pressure of 200 atmospheres?

Lower temperature and higher pressure favours the forward reaction in the Haber process

Explanation:

The equation of the Haber process for the production of ammonia is;

3H2(g) + N2(g) ⇄2NH3(g)

The Haber process involves the combination of hydrogen gas and nitrogen gas in a ratio of 3:1.

In the Haber process, the forward reaction is exothermic, hence the reverse reaction is endothermic. The implication of this is, as temperature is increased, the position of equilibrium moves to the left, and the yield of ammonia decreases. Decrease in temperature will favour the forward reaction. Hence the process is operated at a lower temperature of 450°C.

Secondly, the total number of volumes on the reactant side is 4 volumes whereas the total number of volumes on the product side is 2 volumes. Increase in pressure will favour the direction producing a lesser total volume. Hence increasing the pressure to about 200 atmospheres will favour the forward reaction thus more ammonia is produced