4C CHEMISTRY

• Testing for a carbonate and hydrogencarbonates

  Turns limewater cloudy

  - limewater - saturated aq solution of calcium hydroxide

  - calcium hydroxide reacts with carbon dioxide to form insoluble calcium carbonate (white precipitate)
• Testing for sulfate ions

  add acidified Barium chloride to test for sulfate ions

  - white precipitate of barium sulfate containing sulfate ions will form

  • Bacl2 + SO4 --> BaSO4
• Why is the barium acidified

  - so the acid can react with any carbonate impurities that would form a white barium carbonate precipitate
• testing for halide ions

  - add nitric acid and silver nitrate solution to the substance

  - different colour precipiates will form in halide ion present
• Why do we add nitric acid to silver nitrate when testing for halide ions

  - react with any carbonates and prevent formation of precipitate Ag2CO3
• Testing which halide ion is present in silver halide

  - similar colours so hard to differentiate

  - add ammonia

  - chlorine dissolve in dilute and conc

  - bromine dissolve in conc

  - Iodine does not dissolve in ammonia
• Outline a test to test for ammonium compounds.

  - Add warm sodium hydroxide to form ammonia

  - damp red litmus paper will turn blue