practical 4

• Group 2 ions

  add NaOH dropwise until in excess

  Mg: white ppt Ca: slight white ppt Sr: slight white ppt Ba: no change
• Group 2 ions

  add dilute sulfuric acid dropwise until in excess

  Mg: colourless Ca: slight white ppt : white ppt Ba: white ppt
• ammonium ions

  NaOH, gently heat, damp red litmus paper

  ammonia gas produced turns litmus paper blue
• hydroxide ions

  red litmus paper

  turns blue
• carbonate ions

  add HCl, observe for effervescense

  bubble gas through limewater (calcium hydroxide)

  carbon dioxide produced turns it cloudy
• sulfate ions

  add hydrochloric acid

  add barium chloride

  forms white ppt
• halide ions (aq)

  add nitric acid, then silver nitrate

  Cl: white ppt Br: cream ppt I: yellow ppt

  add dilute ammonia, then concentrated ammonia

  Cl: dissolves in dilute Br: dissolves in concentrated I: no visible change
• halide ions (s)

  add concentrated sulfuric acid

  Cl: white steamy fumes, test gas with damp blue litmus paper = turns red (HCl)

  Br: orange steamy fumes, test gas with filter paper dipped in acidified potassium dichromate solution = turns red/brown (brown gas Br2)

  I: purple steamy fumes and black solid (I2) = test gas with filter paper dipped in lead nitrate solution = paper turns black