Identification of chloride and amphoteric aluminium ions Steps:

• White precipitate with AgNO₃ confirms Cl⁻ ions (AgCl formation).
• No precipitate with Ba(NO₃)₂ after AgNO₃ test confirms absence of SO₄²⁻ ions.
• White precipitate with excess NaOH indicates Al(OH)₃ formation; its amphoteric nature allows dissolution in excess NaOH to colourless solution, maintained colourless upon adding dilute HNO₃. Why A is correct:
• AlCl₃ provides Al³⁺ (amphoteric Al(OH)₃ dissolves in excess NaOH per the reaction Al(OH)₃ + OH⁻ → [Al(OH)₄]⁻) and Cl⁻ (AgCl precipitate), matching all tests. Why the others are wrong:
• B. Aluminium sulfate has SO₄²⁻, forming white BaSO₄ precipitate.
• C. Calcium chloride's Ca(OH)₂ precipitate insoluble in excess NaOH.
• D. Calcium sulfate has SO₄²⁻ (BaSO₄ precipitate) and lacks Cl⁻ (no AgCl).

Final answer: A