Answer is: chlorine anion (Cl⁻) from benzyl chloride (C₇H₇Cl or C₆H₅CH₂Cl) form precipitate (low solubility salt AgCl) with silver cations (Ag⁺) from 2% ethanolic silver nitrate (AgNO₃). Balanced chemical reaction of precipation: Cl⁻ + Ag⁺ → AgCl(s). Benzyl chloride is very reactive colourless liquid.