Chemistry 3B: Testing For Ions

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Chemistry 3B: Testing For Ions.

TESTING FOR POSITIVE IONS:

Flame Test:

Lithium - crimson.

Sodium - yellow.

Barium - green.

Potassium - lilac.

Calcium - red.

Reaction With Sodium Hydroxide:

Aluminium, Calcium and Magnesium ions - white precipitate; Al soluble, Mg insoluble, Ca red in flame test.

Ammonium ions - red litmus turns blue.

Copper (ii) - light blue precipitate.

Iron (ii) - green precipitate.

Iron (iii) - reddish brown precipitate.

TESTING FOR NEGATIVE IONS:

Carbonates:

Add dilute acid, if a carbonate will fizz and produce water and carbon dioxide; can check gas with limewater, goes cloudy with CO2.

Halides:

Add silver nitrate and dilute nitric acid to a compound, if precipitate is: chloride - white; bromide - cream; iodide - yellow.

Sulfates:

Add dilute hydrochloric acid with barium chloride solution; precipitate is the insoluble salt barium sulfate if a sulfate is present.