Tests for ions

• Test for carbonate ions:

  Add dilute HCl - bubble gas produced through limewater- turns cloudy as CO2 produced. Fizzing.
• Test for halide ions:

  Add dilute nitric acid (removes interfering ions) & silver nitrate solution.
• Chloride:


  White precipitate of silver chloride dissolves in dilute ammonia solution.
• Bromide:


  Cream precipitate of silver bromide dissolves in concentrated ammonia solution
• Iodide:


  Yellow precipitate of silver iodide insoluble in ammonia solution
• Test for hydroxide ions:

  (OH-) make solutions alkaline- can use pH indicator or red litmus paper turns blue.
• Flame test:


  Dip nichrome wire loop in concentrated HCl (to clean it) & then into compound. Hold loop in clear blue part of Bunsen burner flame. Calcium= brick red Strontium= red Barium= pale green
• Test for ammonium ions:

  Add dilute sodium hydroxide solution to sample in test tube & gently heat. Red damp litmus paper turns blue as ammonia gas given off.
• Test for sulfate ions:

  Add dilute HCl (removes traces of carbonate & sulfite ions) & then barium chloride solution. White precipitate of barium sulfate formed.
• Precipitate test for group 2 ions:

  Add dilute sodium hydroxide solution dropwise & observe precipitate. Add until excess.
• Magnesium:


  Slight white precipitate- white precipitate in excess OH-
• Calcium:


  Slight white precipitate- same in excess OH-
• Strontium:


  Slight white precipitate- same in excess OH-
• Barium:


  No change in OH- or in excess OH-