Ammonia is manufactured by the Haber process.
(a) Under what condition do the reactants combine to form ammonia? Give a balanced equation for the reaction.
(b) In what ratio by volume, are the above gases used?
(c) state one possible source of each reactant used in the Haber process.
(d) state whether the formation of ammonia is promoted by the use of high pressure or low pressure?
(e) Mention two possible ways by which ammonia produced is removed from unchanged gases
(f) What is the function of:
(i) finely divided iron
(ii) molybdenum in the above process?

AcademicChemistryNCERTClass 10

(a) Conditions for reactants to combine:
  • The optimum temperature is 450°C - 500°C
  • Above 200 atm pressure
  • Finely divided iron as catalyst
  • Traces of molybdenum or Al2O3 as promoters.
Reaction: $N_2 +3H_2 \rightarrow 2NH_3 + heat$

(b) Dry nitrogen and dry hydrogen in the ratio of 1:3 by volume is made to combine.
(c) Source of Hydrogen: Hydrogen is generally obtained from water gas by the Bosch process. 
Source of Nitrogen: It is obtained from the fractional distillation of liquid air.
(d) High pressure favours the forward reaction i.e. formation of ammonia.
(e)Two possible ways by which NH3 produced is removed from unreacted N2 and H2 by
(i) Liquefaction: NH3 is easily liquefiable.
(ii) Absorbing in water: As ammonia is highly soluble in water.
(f) (i) Finely divided iron acts as a catalyst as it increases the rate of reaction.
(ii) Molybdenum acts as a promoter to increase the efficiency of the catalyst.
Updated on 10-Oct-2022 12:46:29