Selective precipitation of barium sulfate

Steps:

• Dissolve mixture in nitric acid to form soluble Mg(NO3)2 and Ba(NO3)2.
• Add H2SO4(aq) to introduce SO4^2- ions.
• Ba^2+ + SO4^2- → BaSO4(s) (insoluble precipitate); Mg^2+ remains in solution as soluble MgSO4.
• Filter BaSO4 solid, leaving Mg^2+ solution for magnesium compound isolation.

Why C is correct:

• Barium sulfate (BaSO4) has very low solubility (Ksp ≈ 1.1 × 10^-10), precipitating selectively from solution.

Why the others are wrong:

• A: Both barium chloride (BaCl2) and magnesium chloride (MgCl2) are highly soluble; no solid forms.
• B: Magnesium chloride (MgCl2) is soluble; no precipitation occurs.
• D: Magnesium sulfate (MgSO4) is soluble; no solid to filter.

Final answer: C