Write the net ionic equation for the reaction of Na2SO4 and BaCl2 in solution; determine the precipitate.

• A. Ba2+ + SO4^2- → BaSO4(s); Precipitate: BaSO4.
• B. Na+ + Cl- → NaCl(s); Precipitate: NaCl.
• C. Ba2+ + 2Cl- → BaCl2(s); Precipitate: BaCl2.
• D. SO4^2- + 2Na+ → Na2SO4(aq); Precipitate: Na2SO4.

Answer: (A)

When soluble salts react in solution, the actual chemical change is the pairing of ions to form an insoluble product, while ions that stay in solution as ions are spectators. Here, Ba2+ from BaCl2 meets SO4^2− from Na2SO4. The combination Ba2+ with SO4^2− forms BaSO4, which is highly insoluble and appears as a solid precipitate. The other ions, Na+ and Cl−, remain dissolved as NaCl and do not precipitate. That makes the net ionic equation: Ba2+ + SO4^2− → BaSO4(s), and the precipitate is BaSO4. The other possible products, NaCl, Na2SO4, and BaCl2, are all soluble and do not form a solid, so they don’t appear in the net ionic equation.