Identification via barium and ammonia solubility tests

Steps:

• Acidification with nitric acid followed by barium nitrate yields no precipitate, ruling out sulfate ions (BaSO4 would form white ppt).
• No visible change confirms absence of other anions like sulfate that precipitate with Ba2+ post-acidification.
• Adding aqueous ammonia produces a white precipitate soluble in excess, characteristic of Zn2+ forming Zn(OH)2 then dissolving as [Zn(NH3)4]2+.
• Thus, X contains Zn2+ and no interfering anions, matching zinc chloride.

Why D is correct:

• ZnCl2 dissociates to Zn2+ and Cl-; Zn2+ gives white Zn(OH)2 ppt with NH3, soluble in excess due to amphoteric nature and complex formation.

Why the others are wrong:

• A. Sodium carbonate: No precipitate with ammonia, as no metal cation forms hydroxide.
• C. Calcium nitrate: Forms white Ca(OH)2 ppt with ammonia, but insoluble in excess (Ca2+ not amphoteric).

Final answer: D