Which of the following will not dissolve in a hot mixture of NaOH and H2O2? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Precipitation with NaCl (Cl-) indicates the cation forms an insoluble chloride, which restricts the choices to Pb2+, Ag+, or Hg22+. Step 2: Reaction with excess ammonia yields a stable white hydroxide/basic salt precipitate with Pb2+, while Ag+ forms a soluble colorless complex [Ag(NH3)2]+ (no precipitate) and Hg22+/Hg2+ undergo blackening. Step 3: Reaction with H2S yields black lead(II) sulfide (PbS↓). Hence, the salt is lead(II) nitrate, Pb(NO3)2, matching option (b).