A colorless aqueous solution contains nitrates of two metals, X and Y . When it was added to an aqueous solution of NaCl , a white precipitate was formed. This precipitate was found to be partly soluble in hot water to give a residue P and a solution Q . The residue P was soluble in aq. NH 3 and also in excess sodium thiosulfate. The hot solution Q gave a yellow precipitate with KI . The metals X and Y , respectively, are
A. Ag and Pb
X = AgNO 3 , Y = Pb NO 3 2 AgNO 3 X + NaCl → AgCl ( P )   ↓ + NaNO 3 AgCl   ( s ) ↓ ( P ) + 2 NH 3 → Ag NH 3 2 + Soluble Cl − AgCl ( P ) + 2 Na 2 S 2 O 3 → Na 3 Ag S 2 O 3 2 Solubel + NaCl Pb NO 3 2 Y + 2 NaCl → PbCl 2 White   ppt   Q ( Soluble   in   hot water )   ↓ + 2 NaNO 3 PbCl 2 aq . Q + 2 KI → PbI 2 Yellow   ppt + 2 KCl
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