Analysis - GCSE Chemistry C3

Some notes on how different chemical tests can show what certain compounds are. If the file doesn't open, let me know.

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Flame tests - put a small amount of the compound to be tested in a platinum wire loop
which has been dipped in concentrated hydrochloric acid, burn in a Bunsen burner
Lithium ­ bright red flame
Sodium ­ golden yellow flame
Potassium ­ lilac flame
Barium ­ green flame
Copper ­ turquoise flame
Magnesium ­ no colour flame
Calcium ­ brick red flame
Testing with Sodium Hydroxide (NaOH)
Magnesium hydroxide - white precipitate
Calcium hydroxide - white precipitate
Aluminium hydroxide ­ white precipitate but then re-dissolves in excess NaOH to form a
colourless solution
Iron (II) hydroxide ­ sludgy green precipitate that slowly turns brown
Iron (III) hydroxide ­ reddish brown precipitate
Copper hydroxide - blue precipitate
Testing for carbonates (add a dilute acid to a carbonate, it fizzes and CO2 is produced)
Copper Carbonate ­ decomposes when heated to give black copper oxide
Zinc carbonate ­ gives yellow zinc oxide when heated, which turns white when cooled
Testing for Halides ­ add dilute nitric acid and silver nitrate solution
Chloride ions ­ white precipitate
Bromide ions ­ cream precipitate
Iodide ions ­ pale yellow precipitate
Testing for Sulphate ions
Add hydrochloric acid and barium chloride solution to sulphate ions in solution and the white
precipitate barium sulphate is formed.
Testing for Nitrates
Mix some of the unknown compound with aluminium powder; add a few drops of sodium
hydroxide solution and heat. If you started with a nitrate it will be reduced to ammonia.
Testing for Ammonia
Add sodium hydroxide solution to a solution of the unknown solution and gently warm it. If
ammonia is given off as a gas, it will turn damp red litmus paper blue


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