Is copper sulphate white?

No. Hydrated CuSO₄·5H₂O is blue. Anhydrous is white; the practical salt in the bottle is blue.

Deep blue with ammonia?

Excess NH₄OH gives tetraamminecopper(II), deep blue.

Group II. Black CuS with H₂S in dilute HCl.

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Class 12 Chemistry Practical

To analyse the given inorganic salt for one acidic and one basic radical.

Experiment	Observation	Inference
Physical examination	Blue crystalline solid (blue vitriol); odourless	Cu²⁺ present, not a white salt
Solubility	Soluble in water giving a blue solution	Hydrated Cu²⁺ ions
Dry heating	Water lost; residue white anhydrous CuSO₄, then black CuO on strong heating	Hydrated copper sulphate
Flame test	Bluish-green flame	Copper indicated
Dilute H₂SO₄	No CO₂	Not carbonate
Conc. H₂SO₄	No halide / NO₂ fumes	Anion is sulphate, not nitrate / halide

Experiment	Observation	Inference
Confirmatory Tests
Barium chloride Acidify the water / soda extract with dilute HCl and add BaCl₂	White ppt of BaSO₄, insoluble in conc. HCl and conc. HNO₃	SO₄²⁻ is confirmed
Lead acetate Acidify with acetic acid and add lead acetate	White ppt of PbSO₄	SO₄²⁻ is confirmed

Experiment	Observation	Inference
Pass H₂S through the original solution acidified with dilute HCl	Black ppt of CuS	Group II (Cu²⁺) may be present
Confirmatory Tests
Ammonium hydroxide Dissolve the ppt in dilute HNO₃. Add NH₄OH dropwise, then in excess	Pale blue ppt dissolves giving a deep blue [Cu(NH₃)₄]²⁺ solution	Cu²⁺ is confirmed
Potassium ferrocyanide Acidify with acetic acid and add K₄[Fe(CN)₆]	Chocolate-brown ppt of copper ferrocyanide	Cu²⁺ is confirmed

The given salt contains Cu²⁺ as the cation (basic radical) and SO₄²⁻ as the anion (acidic radical). The salt is Copper Sulphate (CuSO₄).

Use small quantities of salt and reagents; do not use excess.
Keep the mouth of the test tube away from the face while heating.
Use freshly prepared FeSO₄ for the brown ring test.
Nessler’s reagent is toxic (mercury); handle with care and do not pipette by mouth.

Why is the salt blue?
[Cu(H₂O)₆]²⁺ absorbs in the orange-red and appears blue.
Why black ppt with H₂S?
CuS is very insoluble and black.
Why H₂S in acidic medium?
Group II sulphides ppt even at low [S²⁻]; ZnS would not.
Why deep blue with excess NH₃?
Formation of [Cu(NH₃)₄]²⁺.
Why chocolate-brown ferrocyanide?
Copper ferrocyanide. Zinc ferrocyanide is bluish-white.
Why BaCl₂?
Sulphate anion.
What is blue vitriol?
CuSO₄·5H₂O.
Why does anhydrous CuSO₄ turn white?
Loss of water of crystallisation; used as a test for water.