Describe Properties of Copper Sulphate

Properties of Copper Sulphate (CuSO₄.5H₂O)

Physical properties

1. The anhydrous salt is colourless but the hydrated salt is blue in colour.
2. It readily dissolves in water but is insoluble in alcohol.

Chemical Properties

1. Action of Heat

On heating CuSO₄.5H₂O loses its water of crystallization and decomposes at 720°C to give cupric oxide and sulphur trioxide.

2. Action of ammonia

Copper sulphate gives deep blue colour with NH₄OH forming complex compound.

CuSO₄ + 4NH₄OH → [Cu (NH₃)₄]SO₄ + 4H₂O

3. Action of KI

When KI is added to a solution of CuSO₄, a white precipitate of cuprous iodide is produced.

CuSO₄ + 2KI → Cu I₂ + K₂SO₄ (unstable)

2CuI₂ → Cu₂I₂ + I₂ (white ppt)

4. Action with KCN

A yellow precipitate of cupric cyanide is first formed with KCN and it decomposes to give cyanogen gas.

CuSO₄ + 2KCN → Cu(CN)₂ + K₂SO₄

2Cu(CN)₂ → Cu₂(CN)₂ + (CN)₂ (cyanogens)