Experiment 15: Decomposition reaction


  • Study an example of double displacement reaction

Materials required:

  • Ammonium chloride
  • Nessler’s reagent K2[HgI4]
  • blue litmus paper
  • laboratory stand with clamp
  • burner
  • funnel


  • Take about 5g of ammonium chloride in a test tube
  • Heat the test tube and observe the vapours forming
  • Bring a strip of filter paper dipped in Nessler’s reagent K2 [HgI4] near the tip of test tube. Observe the change in the colour of the filter paper
  • Bring a wet blue litmus paper near the tip of the test tube. Observe the change in its colour


  • Litmus Test - Blue litmus turns red (confirms HCl gas)
  • Nessler's reagent test - Filter paper turns yellow (confirms ammonia)


  • On heating ammonium chloride, ammonia and HCl gas are produced


  • Ammonium chloride on heating in an open container is decomposed into hydrogen chloride and produces ammonia gas. This is an example of decomposition reaction:

NH4Cl(s) --> NH3 (g) + HCl (g)