Testing for negative ions The chemical tests for halides, carbonates, sulfates and nitrates 3.0 / 5 based on 1 rating ? ChemistryTesting and analysing substancesGCSE Created by: Marianne BradleyCreated on: 06-05-09 17:57 Test for carbonate add dilute HCl to the substance Carbonates fizz because they give off carbon dioxide Carry out the limewater test If the lime water goes milky then carbonates are present 1 of 4 Sulfate dissolve sulfate in distilled water Acidify the solution with dilute HCl Put a small amount of solution in a test tube Add barium chloride drop by drop Look for a dense white precipitate - this shows sulfate ions are present 2 of 4 Halide (chloride, bromide, iodide) Dissolve in distilled water Put 2cm depth of halide solution in a test tube Acidify the solution with dilute nitric acid Add silver nitrate solution drop by drop If a precipitate forms, look at the colour to identify the halide: WHITE=CHLORIDE CREAM=BROMIDE YELLOW=IODIDE 3 of 4 Nitrate Dissolve in distilled water Put 2cm of solution in a boiling tube Add a few drops of sodium hydroxide Warm gently to boiling If it smells like ammonia and turns damp red litmus blue, there is an ammonia salt - test won't work properly IF no ammonia - add a pinch of aluminium powder and boil gently A positive ammonia test now shows that a nitrate is present 4 of 4
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