is a process in which solute particles find each other and form a insoluble solid together.
Generally, the chlorides, bromides, and iodides of all metals except lead, silver, and
mercury(I) are soluble in water. HgI2 is insoluble in water. PbCl2,PbBr2,and PbI2 are soluble in hot water.
The sulfates of all metals except lead, mercury (I), barium, and calcium are
soluble in water.
Reaction involved are:
Pb2++2Cl−⟶PbCl2↓
Pb2++2I−⟶PbI2↓
Pb2++SO2−4⟶PbSO4↓
Barium forms precipitate with sulphate ion only, BaCl2 and BaI2 are soluble, hence they won't form ppt.-
Ba2++SO2−4⟶BaSO4↓
HgCl2 is soluble in nature. However, HgI2 is an insoluble compound.
Hg2++2I−⟶HgI2↓
CuI2 is not a stable compound. It immediately decomposes to insoluble copper (I) iodide (CuI) , releasing I2. However, CuCl2 and CuSO4 are soluble in nature. Hence, they won't form precipitate.
Reaction involved:
Cu2++2I−⟶CuI2
2CuI2⟶2CuI+I2
Pb2+ is the only ion to form ppt. with all the given ions.
Hence, the correct option is (A).