Tests for Ions

• Test for acid


  Blue litmus paper turns red
• Test for alkali


  • Small sample on test tube
  • Add red litmus paper
  • Red litmus paper turns blue
• Test for carbonates


  • React with acid to form CO₂
  • (Dilute nitric acid)
  • Bubbles -> could be carbonate, bubble through limewater to see if it is CO₂
• Test for Sulphate


  • Barium Nitrate -> white precipitate
  • Ba²⁺(aq) + SO₄²⁻(aq) -> BaSO₄(s)
• Test for Halides


  • Add silver nitrate -> precipitate forms
  • Ag⁺(aq) + X⁻(aq) -> AgX(s)
• Solubility of Halides in Ammonia

  Cl(white): soluble in dilute NH₃, soluble in conc. NH₃

  Br(cream): insoluble in dilute NH₃, soluble in conc. NH₃

  I(yellow): insoluble in dilute NH₃, insoluble in conc. NH₃
• Sequence of tests


  1. Test for Carbonates
  2. Test for Sulphates
  3. Test for Halides