Test of transition metal ions [Higher tier only]

Solutions containing transition metal ions often have characteristic colours. You are expected to know the colours of solutions containing the following ions:

Fe2+(aq) → pale green

Fe3+(aq) → brown

Cu2+(aq) → blue

[GCSE Chemistry only]

The test for the presence of Fe2+ ions, Fe3+ ions and Cu2+ ions is the addition of dilute sodium hydroxide to a solution of each ion to form a precipitate of the metal hydroxide.

Fe2+(aq) + 2OH(aq) → Fe(OH)2(s) (a dark/dirty green precipitate)

Fe3+(aq) + 3OH(aq) → Fe(OH)3(s) (an orange/brown precipitate)

Cu2+(aq) + 2OH(aq) → Cu(OH)2(s) (a blue precipitate)

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