Silver iodide formation and insolubility in ammonia

Steps:

• Mix aqueous AgNO₃ with KI: Ag⁺ + I⁻ → AgI (s), a yellow precipitate forms.
• AgI is characteristically yellow, distinguishing it from cream AgCl or pale yellow AgBr.
• Add aqueous NH₃: AgI remains insoluble due to weak complex formation with ammonia.
• Observation: persistent yellow precipitate.

Why D is correct:

• AgI is yellow and insoluble in dilute aqueous ammonia, as its stability prevents dissolution (unlike AgCl forming [Ag(NH₃)₂]⁺).

Why the others are wrong:

• A: Cream color matches AgCl, which dissolves in NH₃; incorrect for iodide.
• B: Cream color is wrong; AgI is yellow, not cream.
• C: AgI does not dissolve in NH₃, so yellow precipitate persists.

Final answer: D