Precipitation of Insoluble Barium Sulfate Steps:

• Identify barium sulfate (BaSO4) as insoluble, prepared via double displacement in aqueous solution.
• Select reagents where both are soluble salts, yielding BaSO4 precipitate and soluble byproduct.
• Test option C: BaCl2(aq) + Na2SO4(aq) forms white BaSO4(s) and NaCl(aq).
• Confirm this avoids gases or excess acids, ensuring purity in school lab.

Why C is correct:

• BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq); precipitation of insoluble BaSO4 from soluble ions follows solubility rules.

Why the others are wrong:

• A: BaCO3(s) + H2SO4(aq) → BaSO4(s) + CO2(g) + H2O(l); produces gas, complicating pure solid collection.
• B: BaCl2(aq) + H2SO4(aq) → BaSO4(s) + 2HCl(aq); excess acid risks impure product or solubility issues.
• D: Ba(OH)2(aq) + H2SO4(l) → BaSO4(s) + 2H2O(l); concentrated acid causes dehydration or side reactions, not suitable for pure sample.

Final answer: C