Answer :

Pb2 + is the ion, when combined with chloride ions, CI-, forms an insoluble substance in water.

Answer is (3) - Pb²⁺.


Explanation;


Among the given choices PbCl₂ is insoluble in water. But it can be soluble in hot water. It appears as white precipitate. The Ksp of PbCl₂ is very small. That's why it is insoluble in water.


Fe²⁺ + 2Cl⁻ → FeCl₂ (soluble in water. Forms pale green color solution)


Mg²⁺ + 2Cl⁻ → MgCl₂ (soluble in water. Forms clear colorless solution)


Pb²⁺ + 2Cl⁻ → PbCl₂ (poorly soluble in water. Forms white precipitation)


Zn²⁺ + 2Cl⁻ → ZnCl₂ (soluble in water. Forms clear colorless solution)