Question

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

Answer 1

Answer:

See explanation.

Explanation:

Hello,

Haber process is defined as the widely acknowledged productive process of ammonia by the reaction:

$N_2(g)+3H_2(g)\rightleftharpoons 2NH_3(g)$

Which is carried out in gaseous phase. Thus, by means of the Le Chatelier's principle, it is possible to know that its standard enthalpy of reaction is -45.90 kJ/mol (NIST webbook) for which it is an exothermic chemical reaction, for that reason less ammonia will be produced at high temperature, nonetheless, the temperature should not be too low since the reaction rate significantly decrease, therefore, the optimum found temperature is 450 °C.

Moreover, since there are more moles (3+1=4) at the reactants and less moles at the products (2), increasing the pressure of the reaction increases the yield of ammonia, nonetheless, higher pressures involve the purchasing of more expensive equipment to withstand the high-pressures, for that reason, the best found pressure has been set as 200 atm.

Best regards.

Answer 2

Answer:

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