Test for anions

• Carbonate ions : mix unk compound with dilute acid
• Carbonate ions react with H+ in the acid to form CO2
• CO2 react with limewater to give white calcium carbonate precipitate
• Sulfate ions : add barium chloride solution
• Barium chloride displace the cation in sulphate compound to form white precipitate of barium sulfate
• Halide ions : mix with acidified silver nitrate solution

  silver halide precipitate is formed as a result of displacement reaction
• To be sure of identity of halide, concentrated ammonia solution can be added