Qualitative analysis of iron (II) and iron (III) ions
Qualitative analysis of Fe2+ salt
Common iron II salts include
- Ferrous sulphate: FeSO4.7H2O
- Ammonium ferrous sulphate (NH4)2Fe(SO4)2.6H2O
- Ferrous oxalate. FeC2O4
Qualitative analysis of Fe2+ salt
Addition of dilute sodium hydroxide or ammonia solution
Observation
A dirty green precipitate insoluble in excess turn brown on standing.
Fe2+(aq) + 2OH–(aq) → Fe(OH)2(s)
Confirming presence of Iron II ions
Forms a deep blue solution with potassium hexacyanoferrate III.
Qualitative analysis of Fe3+ salt
Addition of dilute sodium hydroxide or ammonia solution
Observation
Brown ppt precipitate insoluble in excess turn brown on standing.
Fe3+(aq) + 3OH–(aq) → Fe(OH)3(s)
Confirming presence of Iron III ions
Forms a deep blue solution with potassium hexacyanoferrate II.
Forms a red solution with ammonium thiocyanate solution.
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