Question

(a) Name the process used to manufacture ammonia from its elements.
(b) Under what conditions do the reactants combine to form ammonia? Give a balanced equation for the reaction.
(c) In what ratio by volume, are the above reactants used.
(d) State one possible source of each reactant used in the process.
(e) What is the function of:
(i) finely divided iron,
(ii) molybdenum in the above process.
(f) Mention two possible ways by which ammonia produced is removed from unchanged gases.

Answer 1

(a) Haber's process is used to manufacture ammonia from its constituting elements.

(b) Nitrogen and hydrogen combine to produce ammonia under the following conditions:
(i) Low temperature: The optimal temperature lies in the range of 450-500^oC.
(ii) High pressure: It is around 200-900 atmospheres.
(iii) Catalyst: The catalyst used is finely divided iron or molybdenum.
The balanced equation for the reaction is:

${\mathrm{N}}_2+3{\mathrm{H}}_2$ ⇌ $2{\mathrm{NH}}_3+\mathrm{Heat}$

(c) Nitrogen and hydrogen combine in the ration 1 : 3 by volume to produce ammonia.

(d) Source of hydrogen: Natural gas
Source of nitrogen: Air

(e) Finely divided iron and molybdenum are catalysts that increase the rate of formation of ammonia. They are used as promoters.

(f) The two possible ways by which ammonia produced is removed from unchanged gases:
(i) The mixture of ammonia, nitrogen and hydrogen is cooled in a cooling chamber. Ammonia is easily liquefied as compared to hydrogen and nitrogen, allowing it to be collected in the receiver.
(ii) The unchanged gases, N₂ and H₂, are pumped back to compression pump, leaving ammonia free to be removed easily.