test for anions

• carbonate ions • halide ions • sulfate ions

Add dilute acid Bubble the gas released through limewater Limewater turns cloudy if the carbonate ion is present If a carbonate compound is present then fizzing / effervescence should be seen as CO2 gas is produced, which forms a white precipitate of calcium carbonate when bubbled through limewater:

Acidify the sample with nitric acid Add silver nitrate solution AgNO3, A silver halide precipitate forms is a halide ion is present - the precipitate is indicated by the state symbol (s) The colour of the silver halide precipitate depends on the halide ion Chloride ion forms white precipitate of silver chloride Bromide ion forms a cream precipitate of silver bromide Iodide ion forms a yellow precipitate of silver iodide

Acidify simple with dilute hydrochloric acid Add a few drops of barium solution A white precipitate of barium sulfate is formed, if the sulfate ion is present Test can also be carried out with barium nitrate solution

Anhydrous copper sulfate turns from white to blue on the addition of water

A physical test to see if a sample of water is pure is to check its boiling point A sample of the liquid is placed in a suitable container like a boiling tube and gently heated Using a thermometer, you can check if the boiling point is exactly 100º Any impurities will usually rise the boiling point and depress the melting point of a pure substance