Qualitative analysis of copper II ions

Qualitative analysis of copper II ions

Sodium hydroxide solution

Forms a blue precipitate insoluble in excess

Cu²⁺(aq) + 2OH^– (aq) → Cu(OH)₂(s)

Ammonia solution

Forms a blue precipitate  soluble in excess to form a deep blue solution

Cu²⁺(aq) + 2OH^– (aq) → Cu(OH)₂(s)

Then,

Cu(OH)₂(s) + 4NH₃(aq) → Cu(NH₃)₄²⁺(aq) + 2OH^–(aq)

Hydrochloric acid

Color of solution turns from blue to green to yellow.

[Cu(H₂O)₆]²⁺(aq) + 4Cl^–(aq) ↔[CuCl₄]^2-(aq) + 6H₂O(l)

blue                                          green/yellow

Potassium iodide solution

Forms a white precipitate and brown solution

2Cu²⁺(aq) + 2I^– (aq) → 2CuI(s) + I₂(aq)

Potassium hexacyanoferrate II solution

Brown precipitates

Cu²⁺ (q) + Fe(CN)₆^4- (aq) → Cu₂Fe(CN)₆

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