Salts of Ammonia

Specification Point 5.23C:
  • Describe how ammonia reacts with nitric acid to produce a salt that is used as a fertiliser.
  • Ammonia is one of the main raw materials in fertiliser production.
  • Ammonium salts are used as fertilisers and can be produced on reaction of ammonia with acid.
  • The salt produced depends on the acid chosen.
  • Ammonium nitrate, a fertiliser and one of the most important ammonium salts is made by reacting ammonia with nitric acid:

NH3 + HNO3 → NH4NO3

Ammonium Sulfate

Specification Point 5.24C:
  • Describe and compare:
    a) the laboratory preparation of ammonium sulfate from ammonia solution and dilute sulfuric acid on a small scale
    b) the industrial production of ammonium sulfate, used as a fertiliser, in which several stages are required to produce ammonia and sulfuric acid from their raw materials and the production is carried out on a much larger scale (details of the industrial production of sulfuric acid are not required)
  • Ammonium sulfate is another fertiliser which is commonly used in alkaline soils as it forms slightly acidic solutions in soil water, caused by the ammonium ion, NH4+.
  • It is prepared on large scale industrial proportions but can also be prepared in the laboratory.
  • In the laboratory it is prepared by titrating ammonia with sulfuric acid:

2NH3 + H2SO4 → (NH4)2SO4

  • The titration method is used since both reactants are soluble.

Preparation of Ammonium Sulfate in the Laboratory

Aim: 

  • To prepare ammonium sulfate by titration:

2NH3 + H2SO4 → (NH4)2SO4

Materials:

  • Dilute ammonia solution, dilute solution of sulfuric acid, methyl orange indicator
  • Clamp and stand, burette and volumetric pipette, conical flask, white tile

Acid-Alkali Titration setup, Edexcel GCSE Chemistry

Experimental set-up for a titration

Method:

  • Add an exact volume of ammonia to the conical flask and place on the white tile.
  • Add a few drops of indicator and swirl, it should turn yellow.
  • Add the acid to the flask solution drop by drop, swirling the flask in between.
  • Continue until the colour turns red sharply and record the titre.
  • Repeat by adding exactly the same amount of acid but this time without the indicator which is an impurity.
  • Pour the reaction mixture in an evaporating dish and gently heat in a water bath to remove some of the water.
  • Stop heating when the volume has been reduced to roughly one third of its volume.
  • Leave in a dry place so the remaining water evaporates, allowing crystallisation to occur.
  • This may take a few days depending on ambient conditions.

Analysis of results:

  • After a few days ammonium sulfate crystals should appear.
  • Filter to remove any remaining water.

Industrial Preparation

  • The industrial preparation of ammonium sulfate is a large scale operation consisting of several stages.
  • The raw materials are ammonia and sulfuric acid which must first be either produced or purchased.
  • Often they are produced on-site which is more economical than buying them.
  • Ammonia is prepared by the Haber process and sulfuric acid by the Contact process.
  • Both processes require their own supplies of raw materials, energy and equipment.
  • The most common industrial process of manufacturing ammonium sulfate involves filling a large reactor chamber with ammonia gas.
  • Sulfuric acid is sprayed into the chamber from above and ammonium sulfate powder is produced.
  • Another method involves pumping a mixture of ammonia gas and steam in a reactor which contains some sulfuric acid and a concentrated solution of ammonium sulfate. 
  • The reaction is carried out at 60ºC anc concentrated sulfuric is added gradually.

Ammonium Sulfate Production, Edexcel GCSE Chemistry

Diagram showing the multiple steps in the industrial production of ammonium sulfate

Comparing Methods

Production methods table, Edexcel GCSE Chemistry

Edexcel GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.