Is ammonium sulphate odourless?

The solid can smell faintly of ammonia. Treat it as ammoniacal, not odourless.

Confirmatory test for sulphate?

BaCl₂ gives white BaSO₄ insoluble even in conc. HCl.

Group 0. Nessler brown ppt. Stop.

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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	White crystalline solid; ammoniacal smell	Ammonium salt, not odourless
Solubility	Soluble in water	Unlike BaSO₄ / PbSO₄
Dry heating	May give NH₃; residue can leave sulphate	Ammonium sulphate
Dilute H₂SO₄	No CO₂ / H₂S / SO₂	Not carbonate / sulphide / sulphite
Conc. H₂SO₄	No halide fumes	Not Cl⁻ / Br⁻ / I⁻
Flame test	No characteristic colour	Not Ba / Ca / Sr

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
Heat the salt with NaOH solution	Ammoniacal smell; gas turns red litmus blue	NH₄⁺ may be present (Group 0)
Bring a glass rod dipped in conc. HCl near the mouth of the tube	Dense white fumes of NH₄Cl	NH₄⁺ may be present
Confirmatory Test
Nessler’s reagent Pass the gas into Nessler’s reagent (K₂[HgI₄] in KOH)	Brown colouration or brown ppt of basic mercury(II) amidoiodide	NH₄⁺ is confirmed. Stop cation analysis here for ammonium salts.

The given salt contains NH₄⁺ as the cation (basic radical) and SO₄²⁻ as the anion (acidic radical). The salt is Ammonium Sulphate ((NH₄)₂SO₄).

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 BaSO₄ insoluble in conc. HCl while BaSO₃ dissolves?
BaSO₄ is a highly insoluble sulphate; sulphite ppt dissolves with evolution of SO₂.
Why acidify before adding BaCl₂?
To destroy carbonate / sulphite which would also give a white barium ppt.
Why Nessler for this salt?
To confirm the ammonium cation after NaOH liberates NH₃.
Why no brown ring?
The anion is sulphate, not nitrate.
Why Group 0 before sulphate tests?
Anion tests can be done on soda extract; ammonium is still tested on the original salt with NaOH.
Why scratch not needed here unlike Mg?
Sulphate ppt with BaCl₂ comes at once; MgNH₄PO₄ is slow and needs scratching.
Is (NH₄)₂SO₄ used in Group IV?
No. Group IV uses (NH₄)₂S / H₂S in ammoniacal medium. Different salt.
Why white ppt with lead acetate?
PbSO₄ is insoluble.