Solubility Rules for Precipitation Reactions

Steps:

• Apply solubility rules: nitrates (NO3-) are always soluble; most sulfates (SO4^2-) are soluble except for Pb^2+, Ba^2+, Sr^2+; alkali metal salts are soluble.
• Evaluate A: NaCl contains Na+ (alkali metal) and Cl-, both soluble ions.
• Evaluate B: K2SO4 contains K+ (alkali metal) and SO4^2-, soluble combination.
• Evaluate C: Ca(NO3)2 contains Ca^2+ and NO3-, nitrates are soluble.
• Evaluate D: PbSO4 contains Pb^2+ and SO4^2-, lead sulfate is insoluble per rules.

Why D is correct:

• PbSO4 is insoluble in water (Ksp ≈ 1.6 × 10^-8), forming a solid precipitate in reactions like Pb(NO3)2 + Na2SO4 → PbSO4(s) + 2NaNO3.

Why the others are wrong:

• A: NaCl is highly soluble (all Group 1 chlorides dissolve).
• B: K2SO4 is soluble (alkali metal sulfates dissolve readily).
• C: Ca(NO3)2 is soluble (all nitrates dissolve in water).

Final answer: D