Silver nitrate test distinguishes chloride via white precipitate

Steps:

• Acidify with dilute HNO3 to remove interfering anions like carbonate and ensure halide ions are free.
• Add aqueous AgNO3: forms AgX precipitate; color identifies halide (Cl- white, Br- cream, I- yellow).
• X must yield colourless solution post-acidification and white AgCl ppt.
• Test options: only soluble chloride fits both criteria.

Why D is correct:

• NaCl fully dissociates in water to Na+ and Cl-; Ag+ + Cl- → AgCl (white, insoluble per solubility rules).

Why the others are wrong:

• A: CaI2 provides I-; Ag+ + I- → AgI (yellow ppt).
• B: CuCl insoluble in water, yields no colourless solution; Cu(I) unstable in aqueous acid.
• C: PbI2 insoluble, yields no colourless solution; would give yellow AgI anyway.

Final answer: D