Identifying Anions

Chloride Cl (-)

Add dilute nitric acid (to remove any carbonate present), followed by aq silver nitrate

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Observation: White precipitate is formed

ion will form insoluble AgCl(s) with silver ions

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note: Dilute HCl acid cannot be used as the presence of Cl- will interfere with the test

Ag+(aq) + Cl-(aq) → AgCl(s)

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Iodide I(-)

Add dilute nitric acid followed by aq silver nitrate

Observation:

Yellow precipitate formed

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Ion will form insoluble AgI(s) with silver ions

Sulfate SO4 (2-)

Add dilute nitric acid, followed by aqueous barium nitrate

Observation:

White precipitate is formed

note: Dilute sulfuric acid cannot be used as the presence of SO4 (-2) will interfere with the test

Ba(2+),aq + SO4 (-2),aq → BaSO4 (s)

Nitrate NO3(-)

1) Add aq NaOH, followed by small pieces of aluminium foil/powder

2) Warm the mixture and test any gas given off with moist red litmus paper

Observation:

Effervescence is observed

Colourless, pungent gas evolved turned moist red litmus paper blue. Gas is ammonia

The Ion is being reduced by the aluminium metal to form ammonia gas

Carbonate CO3(-2)

1)Add dilute nitric acid

2) Pass of any gas into limewater

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Observation:

Effervescence is observed

Colourless, odourless gas evolved formed white precipitate with limewater. Gas is CO2.

Presence of CO3(2-) will give carbon dioxide gas when reacted with acid.

E.g. CaCO3(-2),s + 2HNO3,aq → Ca(NO3)2,aq + CO2,g + H2O,l

Observations for Carbonate

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Effervescence

Colourless, odourless gas produced, gas forms white precipitate in limewater (carbon dioxide formed)

Observations for Nitrate

Effervescence is observed

Colourless, pungent gas produced, turns red litmus paper blue (ammonia gas)

Observations for Chloride

White precipitate formed

Observations for Iodide

Yellow precipitate is formed

Observations for Sulfate

White precipitate is formed

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