The tests for anions are relatively more complicated as compared to those for the cations. But nonetheless, let's attempt to tackle them all in an organised manner.
If We're Classifying by Reactants Added...
- Point to note: To differentiate between carbonates and sulfates, it is important that you add barium nitrate or lead (II) nitrate first. Why?
- The problem with carbonates is that they form precipitate with any acid added. But carbonates don't react with nitrates. That's why you should add barium or lead (II) nitrate first, because these would produce precipitates BaSO4 or PBSO4 which are insoluble.
If We're Classifying by Reactions...
So yeah, the most memorable traits of each anion:
- Carbonate — Insoluble with any acid added, CO2 gas produced
- Sulfate — White ppt with barium or lead (II) nitrate; soluble in nitric acid
- Chloride — White ppt with Pb or Ag; forms white crystals when heated then cooled
- Iodide — Yellow ppt ftw
- Nitrate — Devarda's alloy, heating, pungent NH3 gas produced
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