Chemical tests

• test for Carbon Dioxide (CO2 )

  turns limewater milky (sparingly soluble Ca(OH) 2 forms insoluble CaCO3 )
• Chlorine (Cl2 ) test

  bleaches damp litmus paper (Cl2 reacts with water to form HCl and HOCl)
• Hydrogen (H2 ) test


  pops with a lighted splint
• Oxygen (O2 ) test


  relights a glowing splint
• Carbonate (CO 3 2- ) test


  add dilute acid; effervescence, carbon dioxide produced
• Sulfate (SO4 2- ) test

  add dilute nitric acid then aqueous barium nitrate. Gives white precipitate
• Chloride (Cl - ) test


  add dilute nitric acid then aqueous silver nitrate. Gives white precipitate. Dissolves in dilute ammonia to give colourless solution (of [Ag(NH 3 ) 2 ] + )
• Bromide (Br - ) test


  add dilute nitric acid then aqueous silver nitrate. Gives cream precipitate. Dissolves in concentrated ammonia but not in dilute ammonia
• Iodide (I - ) test


  add dilute nitric acid then aqueous silver nitrate. Gives yellow precipitate. Does not dissolve in either concentrated or dilute ammonia
• Iron II (Fe 2+ ) test

  add aqueous sodium hydroxide gives green precipitate, insoluble in excess
• Iron III (Fe 3+ ) test


  add aqueous sodium hydroxide gives orange/brown precipitate, insoluble in excess
• Copper (Cu 2+ ) test

  add aqueous sodium hydroxide gives blue precipitate, insoluble in excess. Or add ammonia: gives a blue precipitate which dissolves in excess to give a blue solution
• Calcium (Ca 2+ ) test


  add aqueous sodium hydroxide gives white precipitate, insoluble in excess.
• Aluminium (Al 3+ ) test


  add aqueous sodium hydroxide gives white precipitate which dissolves in excess
• H + (any acid) test

  turns blue litmus red or makes sodium carbonate effervesce (makes CO 2 gas)
• H2O test


  turns white anhydrous copper (II) sulphate into blue hydrated copper (II) sulphate. It also turns blue anhydrous cobalt (II) chloride into pink hydrated cobalt (II) chloride reaction is reversible, colour changes reversed when hydrated salts are heated.
• Test for Unsaturated hydrocarbons

  turns bromine water from orange to colourless.
• Test for aldehydes


  produces a silver mirror from a colourless solution of Tollens' reagent (or produces a red precipitate from blue coloured Fehling's solution (needs heat))
• Tests for organic (and other) acids (carboxylic acid)

  they release CO2 (bubbles of gas are observed) when shaken with sodium carbonate solution
• Test for acid chloride


  gives misty fumes with water
• Test for alcohol


  add acidified potassium dichromate (K2Cr2O7) orange to green (Cr3+)
• Manganate ion change of colour

  when reduced, goes from deep purple to colourless
• test for amines


  turns litmus paper blue (naturally basic)
• test for arene


  burn in air. produces smokey flame and soot.