Test for negative ions

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  • Created by: Jasmin
  • Created on: 17-05-13 11:36
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  • Test for negative ions
    • Carbonates
      • Acid + Carbonate = Salt +H20 + CO2
      • In limewater CO2 reacts with calcium hydroxide - white precipitate of CaCO3 and turns cloudy
      • Bubble gas through limewater
    • Halides (chloride, bromide, iodide)
      • Add dilute nitric acid (HNO3) - removes carbonates form precipitate with silver ions - interfere
      • Then add silver nitrate solution (AgNO3)
      • CHLORIDE: white precipitate of silver chloride Ag+ + Cl- = AgCl
      • BROMIDE: cream precipitate of silver bromide Ag+ + Br- = AgBr
      • IODIDE: yellow precipitate of silver iodide Ag+ +I- = AgI
    • Sulfates
      • Add dilute Hcl - removes carbonates form precipitate with barium ions - interfere
      • Then barium chloride solution
      • White precipitate tells us sulphate ions are present Ba2+ + SO42- = BaSO4

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