Skip to content

Making Ammonia in the Lab

Properties of Ammonia

  • Soluble in water and forms ammonium hydroxide
  • Alkaline gas classification due to this reaction, because aqueous hydroxide ions are produced
  • Considered toxic as hydroxide formed is corrosive and damage cells
  • Very reactive and reacts with acids to make salts

  • Unlike some toxic gases, ammonia has a very pungent smell and instantly recognisable
  • Safe handling of ammonia gas in large volumes usually involve a fume cupboard

Chemical test

  • Damp red litmus paper
  • When submerged in ammonia gas, it turns blue

Synthesising Ammonia

  • Can be synthesised in the lab by heating a mixture of ammonium salt and an alkali
  • Produces ammonia gas with other by-products
  • Ammonia being soluble in water, we can add a desiccant to the reaction to stop this from happening

Method

  • Mix two spatulas of ammonium chloride with two spatulas of calcium hydroxide in a beaker
  • Hold damp universal indicator paper and damp red and damp blue litmus paper above mixture to observe changes
  • Transfer mixture to dry boiling tube and gently warm using a Bunsen burner on a heat resistant mat, collect ammonia gas in a secondary boiling tube mouth facing down
  • Submerge the mouth of the boiling tube holding the collected ammonia gas in a beaker of water
  • Test the water before and after with universal indicator paper, noting any colour change

Results

  • Ammonia gas:
    • Red litmus - blue
    • Blue litmus - blue
    • Universal indicator - blue/purple